(Updated, Dec. 4)

PROVIDENCE – Rhode Island and Michigan were the only states whose populations shrank from 2006 to 2008, according to a study released this week by Michigan State University’s Land Policy Institute.

About 8,000 people moved out of Rhode Island during that time, while about 80,000 people left Michigan, the study said.

Rhode Island had about 1.05 million residents in 2008, a decrease of 20,500 since the state’s population decline began in 2004, according to estimates by the U.S. Census Bureau.

As a share of the peak population, Rhode Island actually lost more than double the amount of residents (1.9 percent) that Michigan did (0.9 percent), according to an analysis by Providence Business News.

From 2005 to 2008, the number of people living in Providence County fell by nearly 7,000. That was the 19th-largest loss among the 3,141 counties in the United States over the three-year period, the study found.

The Land Policy Institute’s researchers examined the economic impact population loss had on Michigan, and said it had worsened that state’s long economic crisis. They estimated the outflow caused Michigan to lose 15,855 jobs and $1.9 billion in economic output, as well as $2.49 billion in home equity value and hundreds of millions of dollars more in labor and property income.

“When people leave town, so does their economic activity,” Soji Adelaja, the institute’s director and the study’s lead author, said in a statement. “This is especially true in a service economy, which depends upon people providing and needing services. The impact of these departures cuts deeper into the economy.”

The unemployment rates in Michigan (15.1 percent) and Rhode Island (12.9 percent) were two of the three highest in the country in October, with Nevada second-highest at 13 percent, according to the U.S. Labor Department.

The Census Bureau projects that Rhode Island’s population will be 10 percent bigger in 2030 than it was in 2000, with the addition of 104,622 residents bringing the total to 1.15 million.

An earlier version of this article, citing the Land Policy Institute, incorrectly said Rhode Island lost about 2,000 residents from 2006 to 2008. After recalculating the numbers, the institute revised Rhode Island’s population loss to about 8,000.