Outcomes from population pressure vary by social and economic sector. Genetically mediated predispositions exert additional pressure. Few behavioral predispositions appear absolutely immutable, so humans select or default into any from among an array of lifestyles, family formation options, and associations. Population growth redistributes income, creating winners and losers. Population growth in the United States has major ramifications for the world economy, the environment, and society. If present trends continue, the population could double in less than seventy years. Environmental constraints are a useful warning, when heeded in time, to exercise marital and reproductive caution. In historical, undisturbed societies, environmental constraints are usually both heeded and anticipated. Immigration policy has a beneficent intent. Demographer William Frey reinforces economic findings by showing that low-skilled black and white Americans flee states that are heavily impacted by immigration. However, recent work suggests that the signal it sends internationally tends to maintain high fertility rates in the sending country.