Population Change Foreign-born Americans and their descendants have been the main driver of U. They also will be the central force in U. If no immigrants had entered the country afterwhen the U. Over the next five decades, the U. Sincewhen the U. Projection Methods The new Pew Research projections are calculated based on immigration rates, birth rates and death rates that are derived from past trends and assumptions about future patterns.
Among the assumptions are that the current slowdown in immigration will last through the decade, but that growth will pick up somewhat after that.
Fertility rates are not projected to rise, but rates will vary by group. Lifespans are projected to improve modestly.
It should be noted that race and ethnicity are fluid concepts that can change through social consensus, personal self-identification or other means Liebler et al.
For more details on assumptions and racial categories, see Appendix A: By comparison, the overall U. Immigrants contribute to population growth because of both their own numbers and their above-average fertility.
Most of those who immigrate are working-age adults, so immigrants are more likely than U. They also have higher age-adjusted birth rates than people born in the U. Livingston and Cohn, The second generation, today representing 38 million children of immigrants, is projected to be a major force driving future population growth.
The foreign-born population has grown more rapidly than the second generation over the past five decades, but the second generation is projected to grow at a faster pace over the next five decades.
The number of second-generation Americans is projected to more than double byto 81 million, when they will slightly outnumber the 78 million foreign-born Americans.
The third-and-higher generations—those born in the U. Five decades ago, the U. All these groups grew in the ensuing 50 years, especially Hispanics, whose numbers grew sevenfold, and Asians, whose numbers rose more than thirteenfold.
The Hispanic population, 8 million inis nearly 57 million in The Asian population, 1. The white population of nearly million grew to million in The black population, 21 million inincreased to 40 million in During the 20th century, the global population saw its greatest increase in known history, rising from about billion in to over 6 billion in A number of factors contributed to this increase, including the lessening of the mortality rate in many countries by improved sanitation and medical advances, and a massive increase in agricultural .
During the 20th century, life expectancy in the United States increased from about _____ to nearly 80 50 The concept of the past as . A Population History of the United States is the first full-scale one volume survey of the demographic history of this country.
It starts with the arrival of humans in the Western Hemisphere and ends with the current century. U.S. Census Bureau, Statistical Abstract of the United States: 20th Century Statistics Section 31 20th Century Statistics This new section presents .
The median age for the second generation, whose parents mainly came during the early 20th-century wave of immigration, was By , the U.S. population was older, with a median age of 38, mainly because of the aging of the large Baby Boom generation. The 20th century was a time of enormous changes in American life.
The beginning of the 21st century seems a suitable time to look back over the past years and see how the United States has developed, for better and worse, during that period of its history.