New studies have challenged the belief that immigration's effect on the economy is either a net gain or wash. The report claims that historically high levels of immigration depress wages, increases the gap between rich and poor, and requires the government to support and educate the immigrants who are often at the bottom of the economic ladder. Supporters of immigration point out that economic studies don't measure all the benefits of immigration and that the conclusion that there are economic costs does not mean that all immigration is bad.
See "Foreign labor: for US, too much of a good thing?", David R. Francis, The Christian Science Monitor, July 21, 2004