The impact of immigration is also driven by its pace and diversity. Almost half the immigrant population arrived within the past 10 years. At the same time, the number of sending countries with at least 100,000 foreign-born residents in the United States rose 21 in 1970 to 27 in 1980 and 41 in 1990. The perceived failure of the newest group of immigrants to adapt as well as previous waves owes at least in part to their recent arrival. The rapid growth of immigrants who do not speak English well, for example, is a consequence primarily of the size of recent flows and not a change in their propensity to learn English.
Immigrant integration increases steadily with length of stay in the United States.
The education and income level of recent legal immigrants remained high through the 1980s and did not decline according to the U.S. census. Legal immigrants, refugees and illegal immigrants are all included in U.S. censuses. But refugees and illegal immigrants have tended to be poorer and less educated on average than other immigrants. As a result, census data on the education, skills, and incomes of all immigrants understate immigrant quality when applied to the legal immigrant population. Changing policy with respect to legal immigrants cannot be expected to change the characteristics of illegal immigrants and refugees.