Within days, India will become the second nation with a population that exceeds 1 billion, according to U.N. demographers. India, with an annual population growth rate of 1.6 percent, adds more people to the world each year than any other country and is expected to overtake China as the most populous nation within 40 years. India’s numbers have tripled in the last 52 years, since it gained its independence from Britain. China and India together are home to more than one-third of the world’s people. The global population is expected to hit 6 billion on October 12, according to U.N. estimates.