U.S. population, 322 million by late 2015, is growing by over 2.5 million per year. According to one study, the country can sustain a population of only 200 million, and that’s only if we cut energy consumption by half.
The key to population stability is a sustained drop in fertility to the “replacement rate” level, where births and deaths offset one another. In fact, Americans achieved replacement rate fertility in the early 1970s, and our native-born population has remained at or below replacement for much of the subsequent period. Yet population hasn’t leveled off, and isn’t expected to level off any time this century. The reason: extraordinary rates of international immigration.
Rising immigration levels, coupled with a declining rate of natural increase (births minus deaths), mean that immigration accounts for a larger share of U.S. population growth now than in any decade since 1900-09...