[Undocumented migrant labor in the United States].

The author identifies two factors contributing to the increase in the number of illegal migrant workers in the United States. The first is the complex system of legal immigration, which contributes to massive evasion. The second is the preference by many employers for hiring illegal aliens. The author concludes that the proposed changes in U.S. immigration laws, even though they include employer sanctions, are likely to prove as ineffective as previous measures adopted in several states some 10 years ago that also penalized employers hiring illegal aliens. It is suggested that the economic pressures leading to large-scale labor immigration will prove stronger than political pressures to control such immigration