You’ve probably heard of peak oil, and maybe even peak fish. But have you heard of “peak middle-aged people”?

That’s right: The Census projects that the aging of the baby boomers is sending the population of 45- to 54-year-olds in the United States into reverse. In fact, that age group reached its near-term peak in 2010. Even as the overall population is expected to grow, we’ll actually have fewer 45- to 54-year-olds in 2030 than we do today:

This demographic shift will almost certainly affect driving trends. According to each of the last three National Household Transportation Surveys, driving peaks in middle age. At age 54, you drive about as much as you did in your late 20s and early 30s … but after that, it’s a long, steady decline. Take a look at this chart of vehicle miles traveled (VMT) by driver age:

This makes intuitive sense: Folks in middle age are near the height of their earning power, are particularly likely to own a car, and often have demands from work or kids that boost their driving. But as people grow older, they’re more likely to retire, and less likely to have to schlep the kids to soccer practice.

But remember, the boomers are a particularly large generation — that’s why they called it a baby boom, after all — so trends among the boomers are likely to have an outsized impact on national averages. And that includes average driving.

To make matters more interesting, right on the heels of the boomers is the much smaller baby “bust” generation, born when fertility rates were falling to post-war lows. The “buster” demographic is currently moving through its peak driving years, but won’t completely fall off the VMT cliff until about 2030.

All else being equal, these two demographic shifts — aging boomers, rising busters — will lead to an overall decline in per-capita vehicle travel. And the aging of the boomers in particular is likely to influence driving trends for the next two decades. In fact, based on Census population projections and National Household Travel Survey data, we expect per capita driving for the adult population of the United States to fall by 6.5 percent through 2030.

That estimate is based on demographic shifts alone. It doesn’t factor in the other trends that may affect driving; shifts in gas prices, blips in birth rates, changes in social values, new patterns of land use, improvements in mobile technologies, and the pace of economic recovery will all affect our propensity to get behind the wheel. Combined, these other forces may overwhelm the demographic shifts. So take these VMT projections as provisional: All else being equal, we expect per capita driving to fall, but it’s seldom true that all else really is equal.

Still, it’s worth remembering: Any VMT projection that doesn’t account for the aging of the boomers is missing an important piece of the story.

But there’s also some really, really bad news. In fact, here’s the most frightening chart I’ve seen in weeks, created by Sightline pal Devin Porter, showing total climate-warming emissions from fossil fuels consumed in the US and China:

Just as US emissions started to moderate, China’s started to skyrocket.  And in both countries, coal has played an outsized role in emissions trends.

In the US, a flattening in demand for electricity, coupled with a shift among electricity generators away from coal and towards natural gas, has been responsible for much of the decline in national CO2 emissions. Today, about 40 percent of the nation’s electricity comes from coal, down from 50 percent just a few years ago. In China, the reverse is true: demand for electricity is skyrocketing, and the vast majority of the nation’s power comes from coal. Even though China has made some impressive investments in renewables, the nation’s coal addiction has simultaneously created a public health crisis and pushed it past the US into the top spot among global climate polluters.

As US demand for coal declines, the coal industry is desperately trying to ship its products to China. But why on earth would we possibly want to make that red line rise any higher—especially when we can take pride in the fact that our own emissions are finally moderating?

Photo by Michael Edson.

I’ve been thinking about upgrading to an electric car for awhile now. And in today’s market, there are plenty of models to choose from.

But having a lot of options makes for a complicated decision! Each model of electric car has its own unique mix of efficiency, charging time, and driving range — and since buying a car is a big decision, I want to find the model that makes the most sense for my family. To add to the confusion, there doesn’t seem to be any single, unified source of information on the many electric car options out there.

So, for my own convenience — and hopefully yours — I pulled together a table with basic stats on the major electric and plug-in hybrid cars:

Click to embiggen. (Sources include the manufacturers’ websites, Wikipedia, FuelEconomy.gov, and Motor Trend Magazine.)

What I took away from this research is that there’s no “perfect” choice among the EVs on the market. They’re all far more efficient in electric mode than gas-only models. That means less money spent on fueling your car, and lower levels of greenhouse gas emissions for each mile driven. But whether you’re willing to pay a premium for a longer range, a faster charge, or a higher top speed seems like a personal choice that I can’t help you out with.

But at least you now have the numbers. Happy comparing!

And now for the notes and caveats:

• I’ve restricted my search to electric and plug-in hybrid sedans that can carry at least four people — which is what my own family needs most days of the week — and to cars that are either on the market right now, or are expected to be offered later this year, in at least some part of the Pacific Northwest. I decided not to include a couple of cars — the Coda and the Toyota RAV4 EV — that are only being sold in California right now. If I’ve missed some cars, let me know in comments and I’ll be happy to update the table!

• MPGe stands for “miles per gallon equivalent” — which is how the Environmental Protection Agency (EPA) rates the efficiency of electric vehicles.

• I sorted the models by base MSRP (manufacturer’s suggested retail price) minus the maximum U.S. tax credit allowed for that model. But note that you only get the full tax credit if you actually owe that much in federal income tax! Also, I decided not to include the cost of installing an in-home 240-volt charger in the vehicle price, since people with ready access to a public charging station might not need one.

• Some of the figures above are estimates, rather than official figures. I did my best, but unfortunately you may need to check the official figures as they’re released.

• The Honda Fit EV isn’t actually available for sale yet. A limited run will be leased to customers in Oregon and California beginning this summer. I’ve included its MSRP price (with tax credit) for comparison’s sake, but folks who lease a Honda Fit aren’t even allowed to buy it after the lease is over. That means that the price I quote is sort of irrelevant at this point.

• Retail deliveries for the Tesla Model S are scheduled to begin in June, but it looks like the smaller-battery models won’t be shipped until late 2012. I wasn’t able to find solid data on 120-volt charging times on the Tesla website, and the 240-volt charging time estimate can be cut in half if you buy an optional “twin charger” for $1,500. The Tesla website quotes a 300-mile range for its 85-kilowatt-hour (kWh) model … but recently announced that its range is 265 miles under EPA’s new test cycle, which, as a reader pointed out, could mean that the ranges for the 40- and 60-kWh models may be slightly overstated — thus the asterisk.

• The MPGe figures for the Prius Plug-in and Chevy Volt are for electric-mode only. The Volt gets 37 mpg in all-gas mode, and the Prius gets 50 mpg.

• And as a reminder, the differences in MPGe in all-electric mode are actually quite small. As we’ve written a number of times, miles-per-gallon math is actually quite deceptive: Differences at the low end of the mpg scale matter much more than do differences at the high end of the scale. So the difference between the top performer (the Honda Fit, at 116 MPGe) and its closest rival (the Mitsubishi MiEV, at 112 MPGe) is actually quite small.

Cross-posted from Sightline Daily.

In a story about the decline of youth car culture, The New York Times quotes an advertising exec on the feelings of today’s youth toward the auto:

“They think of a car as a giant bummer,” said Mr. Martin. “Think about your dashboard. It’s filled with nothing but bad news.”

True dat. I’m not young anymore, but looking at my gas gauge is one of the biggest downers of my day. Though as I’ve argued before, a big part of waning interest in cars among young people stems from economics rather than cultural shifts: Gas and cars are expensive, youth unemployment is high, and young peoples’ wages are down. And besides, new licensing laws have made it more difficult and costly for many teens to get a license, while making driving a lot less appealing. (When I was 16, the lure of cruising around with friends was a major impetus for getting my license — but today licensing laws in many parts of the country forbid teens with new licenses to drive with a bunch of friends.)

Regardless of the reasons, the latest figures show that driving is continuing to decline — not simply among young people, but across the board.

• Year-end federal figures show that total miles logged on U.S. roads fell by a little over a percent last year [PDF]. Adjusting for population growth, that’s a decline of nearly 2 percent per person. Which isn’t a lot, but every little bit adds up. In fact, total vehicle travel in the U.S. was lower in 2011 than it was in 2004.

• The declines in the Northwest — particularly Oregon — began earlier than the national trends, and have cut more deeply into car travel.  By 2010, Oregonians had cut their total vehicle travel to roughly 1998 levels. And measured per person, vehicle travel was at its lowest level since 1986.

I could go on (and on).  But suffice it to say that the data now leave no room for doubt: For all sorts of reasons, people have less appetite for car travel than they did just a few years back. A look at the demographics suggests that these trends could well continue, even as the economy recovers. Baby boomers are aging past their peak driving years, and are being replaced by the much smaller baby bust generation. Gas prices are showing no sign of a sustained drop. And meanwhile, young people just aren’t taking to the roads the way they used to.

It makes me wonder … why is it again that we’re planning to spend so many billions of dollars on big new roads?

Photo: Cyril Plapied

Tuesday’s news carries a story that I’ve been expecting for a while: Connecting Washington, a task force convened by Washington’s governor, has called for $21 billion in new transportation investments over the next 10 years. I haven’t seen the recommendations themselves, only the news report. But it looks like the money would get spread around a bit — with some for ferries and some for transit — but from what I can gather, most of the money would be slated for roads.

So in the upcoming months, I expect we’ll be hearing a lot about how investing in new roads will help clear up traffic problems, particularly in greater Seattle and the Washington side of greater Portland.

But a study that’s been sitting on my desktop for a while — which I count as the single most interesting transportation paper [PDF] I ran across all year — suggests otherwise. Co-authored by researchers Gilles Duranton and Matthew A. Turner from the University of Toronto, it’s a careful and remarkably thorough analysis of the relationship between urban highway space and traffic volumes in the U.S. And its key finding is straightforward:

For interstate highways in the densest parts of metropolitan areas, we find that vehicle kilometers traveled [vkt] increases in exact proportion to highways.

In short, the authors find that building new urban highways simply increases traffic volumes — not in some general, intuitive sense, but in the sense that a 1 percent increase in urban highway space increases urban road travel by precisely 1 percent.

To many folks who follow transportation issues closely, the idea that new roads create new traffic is familiar — yet it sometimes gets bandied about rather casually, as if it’s something that we know but don’t particularly need to prove. But there’s nothing casual about Duranton and Turner’s analysis. It’s thorough, well-thought out, rigorous, employs careful controls to separate cause from effect, and uses the best available data for the U.S. transportation system from (I kid you not) 1835 to the present.

And while road skeptics will undoubtedly be heartened by the findings about highways and traffic, they may be troubled by another of the study’s findings: Public transit has virtually no effect on traffic volumes.

The irrelevance of transit service to urban traffic volumes goes against both intuitions and the claims of many transit analysts. Yes, it’s easy enough to argue that if all transit riders started driving, then they’d clog the roads during rush hour; and conversely, that if a bunch of people switched from cars to buses, rush-hour traffic would get lighter for awhile. But as the authors point out, if drivers switch from cars to buses or trains, it has much the same effect as adding new road space: Traffic clears up temporarily, but faster travel quickly attracts more drivers who take longer trips.

And just to be clear — and before the haters start hatin’ — the authors aren’t arguing that transit is irrelevant to transportation, or that it has no value to society. I certainly believe that transit has substantial value for people who can’t afford a car, can’t drive, prefer not to spend their time behind the wheel, or want to live in a place where road space is constrained. Saying that transit doesn’t have much systemic impact on congestion isn’t the same as saying that transit isn’t a good idea!

So if this study is accurate, then it poses some serious problems for transportation compromises that couple road expansions with transit projects. It’s easy to convince yourself that those kinds of compromises are win-wins — that road expansions will simply ease congestion, and that transit will help keep traffic growth in check. But this research suggests that that sort of compromise is a pipe dream. What matters to highway vehicle miles traveled, according to Duranton and Turner, is how much free road space we create. Just about everything else is a distraction.

I’ll leave the technical details to the avid reader (you really should read it! [PDF]) and simply pull out two quotes that explain some of the the other implications of the research.

We find that the welfare gains for drivers of building more highways are well below the costs of building these highways. This conclusion follows, not from the high elasticity of vkt to roads, but from the fact that new roads do not reduce the cost of travel sufficiently.

Road projects are sometimes sold to the public based on promises that easing traffic congestion will save everyone time. But the study finds that these congestion reductions are short lived at best. The additional people on the road get some value from their trips (otherwise they wouldn’t make them!), but for society as a whole, they find that the cost of new roads tends to outweigh the benefits.

We … identify three important sources for this extra vkt: an increase in driving by current residents; an increase in transportation intensive production activity; and an inflow of new residents.

Interestingly, they find that boosting driving among existing road users is only one way that new roads can induce new traffic. Road space also changes the mix of businesses in a metro area, with more road space leading to more driving-intensive businesses; and they even find that lower commuting costs can attract new residents. The latter effect is small — they find that a 10 percent increase in road space can lead to a 1.3 percent increase in population over a decade, all else being equal — but still significant.

I certainly don’t mean to hold up this study as definitive. It’s only one piece of evidence among many on the effects of transit and road construction on traffic. Yet it’s a particularly well-researched piece — one that folks looking to understand transportation (rather than simply argue about it) would be unwise to ignore.

Photo: Joost J. Bakker IJmuiden

Here’s an interesting study (not free, unfortunately) by University of Washington engineering professor Stephen Muench, reviewing the literature on the energy and CO2 impacts of road construction. His study looks mostly at the construction phase itself, rather than the use of the road. In a nutshell: Manufacturing roadway materials generates somewhere between 60 and 90 percent of the CO2 emissions associated with road building. Transportation of equipment and materials to the job site accounts for 10 to 30 percent, and construction activities at the job site itself account for less than 5 percent of CO2 and energy use.

What I think is so interesting here is that the things that you don’t see matter much more than the things that you do. When I think about road construction, I imagine a bunch of construction equipment: graders, steam rollers, bulldozers, and all the other big energy-hungry machines that fascinated me when I was about 3-years-old. But for greenhouse-gas emissions, construction equipment is just the tip of the iceberg. The most significant energy and CO2 impacts happen elsewhere, in the places where 3-year-olds aren’t allowed to visit: in the factories that make cement and rebar, the mines where we get the raw materials, and the roads and railroad tracks they’re shipped on.

But even if you widen your horizon beyond the job site to the comprehensive impacts of road construction, you’re still just looking at the tip of the iceberg. According to Muench’s review:

Ultimately, roadway construction’s contribution to energy use and emissions associated with transportation is small, by some estimates … in the range of 1/18 to 1/20 that of roadway traffic use.

In short, the impacts of the entire road construction phase are typically little more than a rounding error, compared to the fuel consumed by the cars that drive on the new roads.

A few years back, we took a similar look at the effect of road widening on greenhouse-gas emissions, based on some of the very same studies that Muench uses. And we our study had very similar results: In a crowded urban area, the GHGs from materials and construction are dwarfed by the fuel generated by increased traffic from widened highways.

Still, I often hear discussions of the “construction impacts” of road projects focusing on the construction equipment itself. But those discussions are looking at just the tip of the tip of the iceberg. If you’re really worried about the impacts of new road projects, the smart thing is to focus on where the impacts are biggest: on the cars and trucks that will ultimately fill the roads we build.

How do the Leaf’s emissions stack up?

The Leaf’s a bit pricey, but for many families there are federal tax breaks that can help. And while the car has hit a few bumps in the road — including a recent recall to reprogram the starter, and some complaints about shorter than expected range — the car’s overall reviews have been pretty positive.

But if your main concern is the climate impact of your driving habits, how does the Leaf fare? The EPA label says that the car gets the energy equivalent of 99 miles per gallon — 106 mpg in the city, 92 mpg on the highway. Pretty good, in other words!

But the EPA also says that the car emits “0″ pounds of climate-warming emissions each year. And while this is technically true, it’s also misleading. No, the Leaf doesn’t have a tailpipe spewing carbon-laden exhaust. But the electricity the car runs on doesn’t magically appear out of nowhere. And even in the Northwest, blessed as we are with lots of hydropower, some of the electricity that comes out of our sockets started out as coal or natural gas. So despite what the EPA label suggests, the Leaf does have some climate impact.

How much? Let’s run some numbers to see …

There are probably as many ways of calculating carbon footprints as there are eggheads. So I’ll do my best to explain my estimates, without making things too terribly complicated.

The Northwest Power and Conservation Council says that generating the average kilowatt-hour of electricity (enough to power 10 100-watt bulbs for one hour) in the Northwest produces a little over a half pound of CO2. (See the chart on page eight [PDF].)

But there’s a difference between the average carbon emissions and marginal carbon emissions. The marginal emissions represent what power source gets turned up or down when electricity demand goes up or down just a little bit. The Northwest Power and Conservation Council (NWPCC) estimates that in the Northwest, emissions from marginal electricity average about 0.72 pounds per kilowatt-hour. That’s higher than the region’s average emissions, because natural gas generation tends to be “on the margin” (see page 11 [PDF]).

Of course, not all of the power that gets produced at a generating plant even makes it to your home. Some is dissipated as heat during long-distance transmission, or as it’s distributed from the substation to your home. Based on the latest data from the Energy Information Administration (from this page, access the “Table 10″ spreadsheet for each Northwest state), transmission and distribution losses in the Northwest total about 6 percent.

I thought it would be worthwhile to compare the Leaf with a few examples of gasoline-powered cars. I’ve estimated in the past that the lifecycle emissions from gasoline total 25.77 pounds of CO2 equivalents per gallon, including both CO2 from the vehicle tailpipe as well as the “upstream” and trace emissions from fuel extraction, refining, distribution, and combustion.

So based on all this, how do the Leaf’s emissions stack up? Take a look:

As you can see, the Leaf’s greenhouse-gas performance depends crucially on where its electricity comes from.

Personally, I think that the “right” way to think about the Leaf in the Northwest is the bar in the green: the marginal carbon emissions. And on that measure, the Leaf is a lower-carbon vehicle than the Prius. In fact — and purely coincidentally — the Leaf’s emissions work out to be just about the same as its EPA rating: the equivalent of a gas-powered car that gets about 99 miles per gallon.

But on the other hand, if the electricity that powers the Leaf comes from a coal-fired power plant, then the battery-powered car performs far worse than a Prius. In fact, by these calculations, it’s the equivalent of a car that gets about 30 mpg: better than the average car, but certainly not much to brag about.

I take two things away from all this. First, electric cars in the Northwest appear to be a pretty good deal for the climate. But second — and more importantly — coal-fired power negates all of the climate benefits of electric cars. If power companies in the West were to build lots of coal plants in order to power a fleet of electric vehicles, electric car buyers will be doing the climate no favors. People might as well buy a small-and-efficient car that burns plain old gasoline.

So if you really want to drive green, you ought to focus on getting rid of coal, as fast as possible. What car you drive is important; but where your electricity comes from can make an even bigger impact on the climate.

And a technical note: the NWPCC’s estimates of emissions for gas turbines and coal plants may be a bit low, since they may not include all upstream emissions. That said, their estimates are roughly in line with other life cycle estimates for emissions from electricity generation. Life cycle analysis for natural gas power seems to have particularly wide variation — so take these figures as reasonable estimates, not the gospel truth.

Don’t be confused, we’ve got some good news.Photo: Corie Howell

Great Scott, how did I miss this? Late last month, the EPA released a draft greenhouse gas inventory, showing that net climate warming emissions from the U.S. fell by a whopping 15 percent from 2000 through 2009 [PDF].

A 15 percent decline? Wow. Just wow.

But the story gets even more dramatic. Over the same period, the U.S. population grew by about 9 percent. Combining the two trends, net per capita greenhouse-gas emissions fell by 21 percent over the decade. And most of that reduction occurred prior to 2007 — when the economy hadn’t yet slumped, and before energy prices hit the roof.

In case it’s not clear, these reductions made a huge difference. If we’d kept going at 2000′s per capita levels, the nation would have released about 1.5 billion additional tons of CO2 into the atmosphere in 2009. To give you a sense of the scale, 1.5 billion tons of CO2 is …

• More than the direct annual CO2 emissions from all fossil fuels consumed in homes, businesses, and industries in the entire U.S.;
• Over four-fifths of the yearly CO2 emissions from fueling the nation’s cars, trucks, trains, boats, and airplanes.
• About one and a half times as much CO2 as is soaked up each year by the nation’s forests, grasslands, and other ecosystems.

I’ll dive into the numbers in a moment, but my first reaction to this is simple amazement — not so much at the size of the drop, but more at the fact that it drew so little attention from the press. I might have missed it, but I didn’t even see the story mentioned by major climate bloggers. Why is that? Is climate change now such old news that even a big data release like this elicits only a shrug? Were people afraid to discuss the story, figuring that it would seem like crass gloating over a sour economy? Or has the professional news media become so depopulated that nobody even had time to cover the story?

A few notes on the numbers themselves.

First, like all emissions inventories, this one should be regarded as an estimate, not the gospel truth. That’s especially true since it’s still a draft. In my experience, the EPA’s inventories are comprehensive and use good data, but good doesn’t mean perfect; so I have to assume that some parts contain pretty wide error bars.

Second, a good chunk of the net emissions reductions are due to estimated increase in carbon sequestration by forests — which actually tames my excitement over the trends. I haven’t read deeply enough into the causes for the increase in the sequestration estimates. But sequestration can be a a particularly difficult trend to measure, with the widest error bars. And lots of forces, from weather to temporary shifts in timber and crop prices, can have a huge impact on annual sequestration rates. So while an increase in sequestration is good news, it’s not necessarily a trend that will continue into the future.

Third, there’s a big story that this inventory misses completely. The numbers only cover emissions from within the U.S. itself. So international emissions that are made on our behalf — say, to manufacture goods that we import — are missed entirely. It could be that at least some of the emissions reductions from the U.S. inventory were simply shifted overseas. But it’s anyone’s guess how big that shift really was.

Still, despite these caveats, I’ll take my good climate news where I can take it. And a emissions decline of this magnitude is certainly good news.

Photo: Steve Rhodes

[CORRECTION: As mentioned in the comments under this post on Sightline, this discussion of the "Coase theorem" contains several errors -- most notably, that Coase himself did not present his arguments mathematically. In fact, according to a number of sources, there really is no single "Coase theorem" -- instead, there are several different and somewhat conflicting notions that followers and interpreters of Coase have presented as theorems. For more, please read the comments on Sightline.]

Those inclined to be uncharitable might see the phrase “free-market environmentalism” as somewhere between oxymoronic and greenwashing. But I’m a charitable sort: I believe that people can be sincerely committed to caring for the planet — and also firmly committed to the idea that free market principles offer the best hope of doing so.

And sometimes, markets really can be great tools for advancing sustainability. Consider the problem of overfishing: some great success in fisheries management have come from giving individual fishers a “property right” to a share of each year’s harvest. Once those rights are established and firmly enforced, fishers have incentives to boost future years’ harvests — because an abundant fishery increases the value of their “property” — and also to keep an eye on their neighbors to ensure that they’re not taking too much of a shared resource. As it turns out, giving individuals the incentive to act both as stewards and enforcers can be a pretty effective combination. (This National Research Council report has more details — but I should be careful to note that the study found that transferable fish quotas are no panacea.)

As for fisheries, so for air and water? Free-market environmentalists would say yes: the best way to guarantee clean air and fresh water, they’d argue, is to establish clear property rights for pollution, and let the market sort things out. Many even argue that a property-rights based system could lead to major reductions in pollution, since governments sometimes allow more pollution than people actually want.

But unfortunately, free market sincerity only goes so far: it’s possible to be perfectly sincere and also deeply misguided. And, in fact, that’s the conclusion that this article in the Journal of Economic Issues reaches. The authors, Robin Hahnel and Portland-based Kristen Sheeran, have constructed a convincing case that the key intellectual pillar of free market environmentalism — a bit of theoretical economics known as the Coase theorem — has almost no relevance to how pollution markets would play out in the real world.

So what’s this Coase theorem thing all about?

In a nutshell, Nobel-winning economist Ronald Coase proved mathematically that, with a system of guaranteed pollution property rights and under ideal “free market” conditions, society as a whole would get exactly the amount of pollution that its members want — no more and no less. 

For example, if individuals were granted a “property right” to be pollution-free, then some would be willing to accept cash payments in exchange for allowing a little bit of pollution; and ultimately, after lots of pollution trading, “the market” would decide on how much pollution society as a whole could tolerate. Conversely, if polluters are given the “right” to pollute, then people who wanted to be pollution-free would pay the companies not to pollute — and once again, the market would “decide” how much pollution members of society are willing to pay to prevent. (Remember, I’m just describing this idea, not endorsing it.)

Now, you might think that the level of pollution that society would decide on would depend on how “pollution rights” are distributed — that is, whether polluters are given the “right” to pollute, or potential victims are given the “right” to be pollution free. But Coase’s theorem shows that, under ideal circumstances, the way that “rights” are assigned doesn’t actually affect the environmental outcome. Instead, for any given set of individual preferences and costs, a pollution market will always wind up allowing the same level of pollution, regardless of whether the polluters or the victims are assigned the “rights.” 

And that’s the why free-market environmentalists pay so much attention to Coase: his theorem suggests that, if you really want to figure out what the the “socially optimal” level of pollution — the exact level that free people are willing to tolerate, based on the actual costs and benefits of pollution control — all you need to do is create pollution rights, stand back, and let the market sort things out.

A long line of critics have conceded Coase his mathematical insights, but questioned their relevance. After all, the ideal conditions envisioned by Coase — with firmly enforced property rights, fluid markets, and zero transaction costs — are nearly impossible in practice. 

But Hahnel and Sheeran go several steps farther, building the case that Coase’s theorem is even more deeply irrelevant than previous critics have allowed. Here’s the nickel version of their critique:

• Complete information is impossible: One of the key assumptions of Coase’s theorem is that all parties in a pollution market must be essentially omniscient, aware of all private individuals’ preferences to be pollution-free, as well as the costs of pollution control and the potential profits and losses for private firms. That kind of omniscience not only goes beyond what’s realistic, it even exceeds the assumptions of other areas of economics — which tend to assume that economic actors are merely “self-aware” rather than omniscient. 

• Without complete information, Coase’s theorem breaks down: Coase’s math suggests that there’s a single “socially optimal” level of pollution that any set of free negotiations will achieve. But once participants in a pollution market start playing their cards close to their chest — say, by claiming that pollution controls will put them out of business — then all bets are off. All sorts of different pollution levels and prices could result from pollution negotiations, depending on how the market plays out under conditions of incomplete information. And that dashes all hopes for having market forces discover a single “socially optimal” level of pollution.

• Coasean negotiations aren’t markets: To achieve mathematical rigor, Coase simplified pollution negotiations to the simplest case: one polluter and one victim. But with just two parties, you don’t have a market at all! Instead, you’ve got a bilateral negotiation, also known as a “divide-the-pie” game. And those kinds of games, many different price and pollution levels are possible, depending on the specifics of how the negotiations are conducted. Hahnel and Sheeran quote fellow economist Joseph Farrell to explain: “if bargaining and negotiation are perfect (that is, produce perfect outcomes) then the outcomes are perfect. [But] actually, negotiation is far from perfect, even in the simplest situations.”

• Multiparty negotiations make things even more complicated: Standard discussions of the Coase theorem point out that multiparty negotiations can increase “transaction costs” — i.e., costs for running parallel negotiations, or for deciding which people are genuinely victims, and to what extent they’ve been harmed by pollution. But even more troublesome, multiple parties create a host of “tragedy of the commons” complications which make it nearly impossible to believe that market forces alone will arrive at the “socially optimum” level of pollution, with many firms or private individuals “free riding” in the more virtuous actions of their neighbors. Hahnel and Sheeran argue that multiparty problems are so severe that they can’t be simply explained away as higher transaction costs.

All told, Hahnel and Sheeran build a substantial case Coase’s theorem has very little to do with the actual workings of real-world pollution markets. Absent other democratic institutions and meaningful oversight, “free” pollution markets quite likely would allow far more pollution than people actually want. And if you buy this line of reasoning, you have to demote the Coase theorem from one of the pillars of an entire world view to a quirky but not particularly relevant bit of theoretical math.

Now, I’m sure that a single paper won’t be enough to shake free market environmentalists’ faith in their ideology. But for those who aren’t already committed to the that faith, Hahnel and Sheeran give every reason to believe that free market environmentalism is like so many other “isms” — beautiful and elegant on paper, but so divorced from reality that it offers very little to recommend itself in practice.

You might think that vehicle safety studies are all about the crash dummy tests you see on TV, with simulated collisions. But those kinds of tests don’t tell you how often collisions occur. A car that does well in a simulated crash test might not actually be all that safe in the real world, particularly if it’s bulky and hard to maneuver on on the road. 

And that’s what Dr. Tom Wenzel of the Lawrence Berkeley National Laboratory has pointed out repeatedly over the past decade: Bigger vehicles like SUVs aren’t always safer vehicles. 

There’s a lot of food for thought in Wenzel’s report from last March on the relationship between vehicle size and safety [PDF] — which, as far as I can tell, is the most comprehensive and best-documented review of the relationship between vehicle size and real-world safety records.

This study is his most sophisticated look at the topic to date, since it looks not only at real-world crash and fatality records of different makes and models, but also at the kinds of drivers who are involved in the crashes, as well as the the kinds of places that crashes occur. Not too surprisingly, he finds that young males and elderly drivers crash more than the average driver. 

Crash fatalities are more common in rural areas than in urban areas;  in fact, measured by fatalities per vehicle, the densest urban areas are also the safest places to drive. (See the chart to the right; click it to enlarge). But Wenzel is mostly interested in the inherent safety of the vehicles themselves – so his analysis excludes crashes in the most rural and most urban areas, and among higher-risk demographic groups.

The end result is a nuanced take on the relationship between vehicle size and vehicle safety. For example, he finds that …

• Heavier cars do, in fact, tend to be safer than lighter cars;

• Midsized cars are slightly safer than mid-sized SUVs, and compact cars are on a par with small SUVs.

• “Compact SUVs” based on car-body designs are actually safer than the larger, heavier fullsize SUVs based on truck designs;

• For vans, pickups, and fullsize SUVs, gains in safety to drivers are typically offset by increased risks to drivers of other vehicles; and

• There’s a lot of variation in the data: The size of vehicle is just one factor among many when trying to choose a safe car.

(Most of these findings are taken from Figure 4-6 and Figure 4-7 in the report.)

In short, Wenzel finds that there is a relationship between vehicle size and safety — but it’s a different relationship for different kinds of vehicles. People who chose a big SUV because it seemed “safer” than a car in a collision were often making a bad decision; a smaller CSUV, or even a large car, might have offered a safer ride.  Similarly, people who chose a big SUV over a smaller one for “safety” reasons were often just increasing the risks they pose to other drivers.

But perhaps the biggest lesson of all is in the chart above: If you want to stay safe, your best bet is to live in a place where you don’t have to drive much. The casualty differences between a compact urban neighborhood and a suburb are much greater than the relatively minor safety gains from getting a slightly bigger car. Which suggests that if you really want to drive safely, your best option is to drive less.