“While there is growing recognition that migrants can build cross-border social capital, that increasing cultural diversity can provide impetus for the stimulation of entrepreneurship, or that culturally diverse work forces are among the most profitable, the overall perception of migrants in many societies tends to be negative,” the report said.

Mr. Swing said migration was “highly desirable” if managed intelligently and humanely, calling it “both a reality and a necessity.”

The report also reviewed migration trends and major policy developments in the 2010-11 period.

Despite a common perception in the news media that Europe “risked being swamped by a flood of migrants from Africa,” it said that the percentage of Africans migrating abroad remained relatively modest in 2010, when 64 percent of sub-Saharan African migration took place within the region itself.

In all, about 30 million Africans, or 3 percent of the population, live abroad, according to the World Bank.

Meanwhile, foreign workers in Europe suffered higher unemployment in 2010 than their counterparts in the citizenry. While Spaniards suffered 18.1 percent unemployment in 2010, the rate for foreigners in Spain was 30.2 percent, the organization’s data show. In Germany, migrants were nearly twice as likely as locals to be jobless (12.4 percent versus 6.5 percent) during the summer of 2010. Europe, for its part, was the generator of new outflows, with net emigration from Ireland reaching 60,000 people at the end of 2010, after 7,800 in 2009.

The United States was host to about 43 million foreigners in 2010, representing 13.5 percent of the total population, according to the World Bank. About 11.6 million came from Mexico, according to the Pew Hispanic Center. The estimated number of irregular migrants in the United States was steady, at 11.2 million in 2010, after a two-year decline from a peak of 12 million in 2007, the report quoted the Pew Hispanic Center as saying.