"Legal immigration to the United States has increased sharply in recent years, and shows no signs of slowing down. The question of why immigration has grown so rapidly and the implications of this growth for the future are expected to be issues in the 105th Congress. Primarily because of legislation enacted in 1980 and 1986, the numerical restrictions of the basic family and employment-based immigration preference system became less significant. The growth in legal immigration during the past 15 years came in three groups admitted outside these numerical limits -- legalized aliens, refugees, and numerically exempt immediate relatives of U.S. citizens. For example, about 2.8 million illegal or undocumented aliens were 'legalized' between 1981 and 1995."
CRS Report for Congress, 97-230