Nigeria, Ghana and Kenya were the biggest sources of migrants to Europe and the United States among the dozens of nations south of the Sahara, according to the Pew Research Center, a polling and demographic research group in Washington, Reuters wrote.
The large-scale movement of people out of sub-Saharan Africa has grown steadily nearly every year since 2010, the Pew study said.
Global migration overall has strained resources in host countries that are struggling to shoulder the costs. In some places, migration has fueled political tensions and calls for the closing of borders.
Refugees, meanwhile, leave homelands that offer few job prospects, low wages and the dangers of conflict, political instability and modern day slavery, the study said.
Millions more people from the Sub-Saharan region indicated that they would leave if they could, according to Pew findings from six countries.
"The survey results do indicate a certain restlessness among people who want to leave their countries or plan to in the next years," Phillip Connor, senior researcher of the report, told the Thomson Reuters Foundation.
But not all of those will necessarily follow through and move, he added.
More than a third of people surveyed in Senegal, Ghana and Nigeria said they had actual plans to move in the next five years, according to the report.
Nearly 2 million residents of Ghana - 6 percent of its population - applied for a US diversity lottery in 2015, it said.
Restricted to 50,000 people worldwide, the lottery also drew strong interest in the Republic of Congo, Liberia and Sierra Leone.
Europe saw an influx of at least 1 million people from sub-Saharan Africa, most of whom headed to the United Kingdom, followed by France, the report said. Most were asylum applicants.
More than 400,000 sub-Saharan refugees went to the United States, according to the report.
Pew used data from Eurostat, a European statistical agency, the US Department of Homeland Security, the US State Department, and its own polling.
Many more people - nearly 5 million - have moved to other sub-Saharan countries since 2010, mostly as refugees, the report said.