The percentage of African Immigrants in the U.S. has almost doubled every decade since 1970, with immigrants from Nigeria, Ethiopia, Egypt, Ghana and Kenya accounting for nearly half of that population, according to a new Pew Research Center analysis published Monday.

The data, which is based on U.S. Census information, found that there were 1.8 million African immigrants living in the U.S. in 2013, an increase from 881,000 in 2000, and an even greater rise from only 80,000 African immigrants in the U.S. in 1970.

“The growth is evident among recently arrived immigrants,” the analysis stated. “When compared with other major groups who arrived in the U.S. in the past five years, Africans had the fastest growth rate from 2000 to 2013, increasing by 41 percent during that period.”

Although African immigrants account for a small amount of the immigrant population in the U.S., 4.4 percent in 2013, they are the most rapidly growing Black immigration population, increasing by 137 percent from 2000 to 2013.

“The transatlantic slave trade beginning in the 16th century brought hundreds of thousands of enslaved Africans to the U.S., but significant voluntary migration from Africa is a relatively new trend,” the analysis stated.

Some factors that have contributed to the rise are the “Refugee Act of 1980”, which made it easier for those fleeing conflict-ridden areas, such as Somalia and Ethiopia, to resettle in the U.S., as well as “the diversity visa program” – an act passed in 1990 to encourage immigration from underrepresented nations.

Somalia, the Democratic Republic of Congo, Sudan, Eritrea and Ethiopia were five of the top 10 countries for refugee arrivals in 2013.

The largest numbers of African immigrants have settled in New York, California, Texas, Maryland and New Jersey. Each state is home to at least 100,000 foreign-born Africans. Washington, D.C., Maryland and Maine also have sizable African Immigrant populations.