"Give me your tired, your poor, your huddled masses yearning to breathe free," wrote Emma Lazarus, in a poem that still puts a lump in my throat. I'm proud of America's immigrant history, and grateful that the door was open when my grandparents fled Russia.

In other words, I'm instinctively, emotionally pro-immigration. But a review of serious, nonpartisan research reveals some uncomfortable facts about the economics of modern immigration, and immigration from Mexico in particular. If people like me are going to respond effectively to anti-immigrant demagogues, we have to acknowledge those facts.

First, the net benefits to the U.S. economy from immigration, aside from the large gains to the immigrants themselves, are small. Realistic estimates suggest that immigration since 1980 has raised the total income of native-born Americans by no more than a fraction of 1 percent.

Second, while immigration may have raised overall income slightly, many of the worst-off native-born Americans are hurt by immigration -- especially immigration from Mexico. Because Mexican immigrants have much less education than the average U.S. worker, they increase the supply of less-skilled labor, driving down the wages of the worst-paid Americans. The most authoritative recent study of this effect, by George Borjas and Lawrence Katz of Harvard, estimates that U.S. high school dropouts would earn as much as 8 percent more if it weren't for Mexican immigration.