Rapid growth in Minnesota’s black population may well explain what appeared at first to be a sudden drop in that group’s prosperity.

The number of black residents increased by nearly 40,000 in just the past four years, a bigger increase than occurred in the state’s white population.

The number of people who reported difficulty speaking English also jumped sharply in a single year, providing one of the clearest indicators of why median black household income slumped between 2013 and 2014.

“It seems as if population growth at the lower end of the income distribution — less than $35,000 a year — and very little growth at the upper end brought the median down,” said state demographer Susan Brower.

Demographers caution that income estimates can bounce up and down from year to year. Nevertheless, the release of census data last fall showing a growing income gap between blacks and whites stunned state leaders such as Gov. Mark Dayton, who proposed a special legislative session partly to address the issues of black poverty and unemployment.

Prospects for a special session have faded, but legislators are expected to take up the issue when they convene in March.

Graphic: Language and education barriers Graphic: Language and education barriers

The census release helped spur deep data dives by several researchers, including those in the state demographer’s office. The fine-grained data released this month are “really exciting” for social scientists, said Craig Helmstetter, head of the research unit at the Wilder Foundation.

“It’s almost like sequencing a new segment of the genome.”

State is especially complex

Several researchers stress that broad-brush examinations of categories like “blacks” or “Asians” conceal as much as they reveal, because they combine what can be split into 17 different cultural groups with their own histories, challenges and touches of hope.

Some groups are vastly younger than whites, 20 years on average, so one wouldn’t expect them to be earning as much. But even experienced researchers are startled by the high rates of disability in some minority groups — perhaps due to overseas trauma or, in this country, disadvantaged conditions from birth.

The complexities here are greater than in most states, because Minnesota long has been one of the nation’s leading magnets for refugees, who can differ dramatically from other people of color.

Some researchers said that the fragmented nature of Minnesota’s communities of color and the movement of people make it perilous to interpret year-to-year changes such as the apparent drop in black incomes that triggered last year’s controversy.

As for nonimmigrant African-Americans, Helmstetter said that one of the most striking new findings is the fact that half of those in Minnesota were born in another state — twice the rate for all U.S.-born Minnesotans.

The apparently high rate of arrivals from other states, he said, “may be very pertinent to important policy discussions now being had, related to the especially low income of our state’s African-American population.”

Samuel Myers Jr., the Roy Wilkins Professor of Human Relations and Social Justice at the University of Minnesota, said the new data sketch a needlessly negative picture for native-born African-Americans. They ought to include mixed-race blacks, who would raise the group’s success rate, he said.

Brower disputed Myers’ contention, pointing to numbers showing that median income rises by only a few hundred dollars when those 80,000 residents are added in. But Myers said those numbers confirm his point, considering that unemployment drops from 13 to 9 percent after that adjustment.

Recent research is yielding some encouraging signs as well — even for the poorest of refugee groups, whose children are entering college at rates that are striking, given their troubled pasts.

For instance, the college enrollment rate among young Somali-Americans tops that of other black Minnesotans. A Swedish economist who studies African immigration to his own nation came to Minnesota and was “blown away by how well Somalis are doing here,” Brower said.

“He says it’s unheard of for Somalis in Sweden to go to college or grad school — it just doesn’t happen — while here people don’t think it’s unusual,” she said.

The data show that the Hmong, who arrived long before the Somalis, are still on a gradual climb, said Mark Pfeifer, a research analyst at the Hmong Cultural Center. Their poverty rate of 27 percent is high, although Pfeifer said it was 70 percent in 1990 before falling to the mid- to high 30s by 2000.

Even though newcomers from overseas kept arriving, Pfeifer said, he watched the poverty rate melt away year by year until the Great Recession of 2007-09, when progress stalled.

The demographer also took care to note actual numbers, as opposed to rates, in a state that remains overwhelmingly white.

For example, whites account for about 350,000 of the 600,000 Minnesotans in poverty. But in terms of rates, the highs and lows are remarkable: 85 percent of Minnesotans from India have college degrees, while 39 percent of Mexican-Americans in the state lack a high school diploma.

Many of those examining the new numbers note the disturbingly high rates of disability among middle-aged (45-64) Hmong and African-Americans, roughly one-third in each group and a factor in their overall prosperity.

“That really struck me,” Pfeifer said. “But no surprise — we work with a lot of those people here,’’ he added, referring to the Hmong. “It’s related to the Vietnam War and then living in refugee camps so many years, high rates of depression and physical disabilities.”

‘Always a way’

In human terms, the data capture a phase in the life cycles of people such as Kowsar Mohamed, 19, a University of Minnesota student and lab assistant. Her single mom works as a personal care assistant and the family lives close to the poverty line.

“We just purchased our first vehicle in August,” she said. “She never thought it was a big deal, but I was like, ‘Please, please, please, please!’ ”

Her friend Muhubo Mohamed, 20, also a U student, reports that all three kids in her family made it to college, though her brother, aided by a baseball scholarship — a detail that makes both friends laugh — has since dropped out.

Both women are pursuing global studies and are hopeful in much the same way that previous generations of immigrants kept the faith as they worked their way up.

“God willing, there’s always a way,” Muhubo Mohamed said. “I hope to prosper and to help my family — to allow my mom to go back [to Somalia] if possible.”