for the past century and numbered an estimated 5.8 billion in 1996. In 1990, the U.S. population accounted for 4 percent of the world's population (see Table 3.1). Since 1950, the U.S. population has been declining as a proportion of the world's population, decreasing from 6 percent in 1950. If we rely on the world population projections prepared by the United Nations (1995), anticipating results for the United States that are discussed later, the population of the world and the United States will grow through the year 2050.

Because we project that the United States will experience moderate population growth for the next six decades, its proportion of the world's population will remain constant at 4 percent. Some other regions, such as Europe, will account for a diminishing proportion of the world's population over the next six decades, and regions such as Africa are likely to increase their relative proportion.

Although not everyone outside the United States wishes to or realistically will seek to emigrate to the United States, these results also provide evidence that the number of potential U.S. immigrants will increase in the future.