National projections of population growth vary more widely than at any time in history. In some countries, population has stabilized or is declining; but in others, population is projected to double or even triple before stabilizing. In 32 countries, containing 14 percent of world population, population growth has stopped. By contrast, Ethiopia's population of 62 million is projected to more than triple to 213 million in 2050. Pakistan will go from 148 million to 357 million, surpassing the U.S. population before 2050. Nigeria, meanwhile, is projected to go from 122 million today to 339 million, giving it more people in 2050 than there were in all of Africa in 1950. The largest absolute increase is anticipated for India, which is projected to add another 600 million by 2050, thus overtaking China as the most populous country.
New diseases are not the only threat to demographically fatigued countries. Because population growth affects so many dimensions of a society, any of several different stresses can force a country back into a primitive stage of development. For example, in many developing countries food supplies are threatened by aquifer depletion. Recent growth in food production and population in India, a country heavily dependent on irrigation, has been based partly on the unsustainable use of water. Nationwide, withdrawals of underground water are at least double the rate of recharge and water tables are falling by 1 to 3 meters per year. It is estimated that as India's aquifers are depleted, its grain harvest could fall by as much as one fifth. In a country where food and population are precariously balanced and which is adding 18 million people per year, such a huge drop in food output could create economic chaos.