Between now and 2050, the population of Japan is projected to decline by nearly 25 percent. Demographers think Russia will shrink by 20 percent; Germany by almost 10 percent, Italy by 9 percent. But in the United States, it's a much different story. According to the Census Bureau, the U.S. population could grow by nearly 50 percent between 2000 and the mid-point of this century. And nearly half of that growth will occur among Hispanics. Census Bureau Projections

Although not much talked about, this fundamental dynamic -- continued population growth in the United States, fairly rapid decline in much of the rest of the developed world -- is central to the current debate over immigration. A sharp ratcheting down of immigration numbers would quickly change this growth picture in a way many would find disquieting.

The Census Bureau projections suggest minority populations will be the only ones growing by the middle part of the century. Between 2040 and 2050, the numbers indicate, the number of non-Hispanic whites will be on the decline. Even so, largely because of Hispanic growth, the nation's overall population will be up more than 7 percent during the decade. And by 2050, the non-Hispanic white majority will be barely that, with 50.1 percent of the population (compared to almost 70 percent today).