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.
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."