India’s population is expected to hit 1 billion tomorrow, making it the second country to pass that mark. China, which now has an estimated 1.3 billion citizens, was the first. Although India had the first official family-planning program in the developing world, the nation is still growing by 15 million people a year. Half of India’s adults are illiterate, more than half of its children are undernourished, and a third of its people live below the poverty line, according to the Worldwatch Institute. The Indian government will mark tomorrow’s occasion — which it says is cause for neither celebration nor condemnation — with an address from Prime Minister Atal Behari Vajpayee, the unveiling of a commemorative stamp and coin, and the printing of railway tickets with a message on the back encouraging one-child families.