Those earlier immigrant groups generally prospered here and were instrumental in the building of America's economic might. How about this latest fourth wave? Since 1980 about 20 million immigrants have come, with about three of four arriving from Asia and Central America. Over the past quarter-century the percentage of the U.S. population that is foreign born has about doubled from 6.2% in 1980 to 12% today--which means that about one in eight of us is an American by choice, not by birth.

This large influx of new Americans has intensified calls inside and outside of Congress for closing the Golden Gates. Groups ranging from the Federation for American Immigration Reform to National Review magazine have gained political traction by arguing that we need a "time out" on immigrants because they displace American workers from jobs, depress wages and raise welfare and other social service costs.

Yet the evidence for these claims is contradicted by the actual bullish U.S. economic performance during this era of high immigration. One can only marvel at how over the past 20 years the U.S. free-market system has absorbed millions of new immigrants into the economy and labor force almost seamlessly. The 1980s and '90s were two of the fastest economic growth decades in American history, in overall and per capita GDP growth, at the very time when immigration was peaking. Financial and housing assets in the U.S. have more than quadrupled in real terms since the early 1980s, making the past 20 years the most rapid period of wealth creation in American history. Immigrants may not have caused this burst of prosperity, but they certainly didn't prevent it.

George Borjas of Harvard University has claimed that immigrants contribute to the widening income gap between the rich and poor in America. But not only has median real family income in the U.S. risen by 21% since the early 1980s to $52,000 today, but incomes even rose for Americans in the bottom 20% over the 1980-2000 period. This is not to deny that immigrants compete with American workers in some industries and in localized labor markets. Portuguese fishermen, African cab drivers, Chinese textile workers, and Mexican field hands, for example, often do displace American workers and push wages downward. On a macro-level, however, there is no evidence of wage suppression by immigrants, because natives have generally migrated into other professions with higher wages.

Even more encouraging news comes from recent Census Bureau data on the economic advancement of immigrants themselves. The longer that immigrants are here, the better they do financially. For example, immigrants who have been in the U.S. for less than three years have a 7.4% unemployment rate. That rate of joblessness falls to 6.7% after 10 years here, then below 6% after 20 years. The income numbers show the same picture of immigrants climbing the ladder of economic success. New arrivals have a median family income of $31,930. For those who came in the 1990s there incomes average $38,395. And for those who have been here 20 years or more, family income approaches $50,000. Immigrants are economic investments with increasing rates of return over time.

For those of us who believe that the melting pot is a vital and unique feature of American society, this finding that the new immigrants are integrating into our modern economy is highly reassuring. Even more encouraging is the knowledge that a generous immigration policy can coexist with high rates of economic growth and low unemployment. The nativists have gotten this story all wrong for at least the past 20 years; perhaps it would be wise to stop listening to them.