The average size of U.S. households has been declining for decades, but may have grown in recent years, at least in part because of an increase in multi-generational households. Data from the 2010 Census will supply additional information about whether, where and why this is happening.

Meanwhile, here is an early clue: Average household size in Maryland, which had declined in the 1970s, 1980s and 1990s, grew by a tiny amount from 2000 to 2010, according to numbers analyzed by the Maryland State Data Center. In 1970, average household size was 3.25 in Maryland; in 1980, it was 2.82; in 1990, 2.67; in 2000, 2.61. In 2010, it was again 2.61 (the 2000 and 2010 numbers look the same, but the data center analysis shows there actually was an increase of .01 before rounding). Household size grew in several large suburban counties, according to the analysis.

The Census Bureau plans to release statistics on household size in May, but they can be calculated now based on other data released by the bureau this week. To accommodate states such as Maryland that want to take account of prison populations in legislative redistricting, the bureau released detailed counts of populations for group quarters (including prisons). If group quarters counts are subtracted from the total population counts released earlier, the number of people living in households can be derived, then divided by the number of occupied housing units included in the bureau’s recently released redistricting files to produce average household size.