Tax bases in Montgomery and Prince George’s counties shrank a bit in 2010 as the wealthy moved away from the Washington-area suburbs, according to the most recent Internal Revenue Service tax data.

Montgomery County’s tax base decreased by 0.07 percent, or $22.1 million in gross aggregate income, from 2009 to 2010. And Prince George’s County lost $51.4 million, a 0.27 percent decrease in its tax base, according to an analysis by Change Maryland, a grassroots advocacy group that blames the losses on Maryland’s tax policies.