Published: November 01, 2009 11:39 pm      

Census: Maryland family trends vary widely by county

WASHINGTON — If you live in Baltimore City, you are probably not married. If you are a woman between 15 and 50 living in St. Mary’s County, you are more likely to have given birth to a child recently than if you lived anywhere else in Maryland.

These are just two of the findings from a Census Bureau data analysis released last week. The data stem from the agency’s American Community Survey, a continuous effort to obtain accurate numbers on American life at the national, state and local level between the 2000 decennial census and the next one in 2010. The agency released one-year data for 2008 several weeks ago, and just published new data based on three-year averages of various social, economic and demographic factors. The data were collected from January 2006 to December 2008. Since the new numbers combine data from three different annual samples, they are more reliable than those from each annual survey taken individually, Census Bureau spokesman Robert Bernstein said.

According to the averaged data, the fertility rates for Maryland women vary widely based on their home county. For every 1,000 women between 15 and 50 living in St. Mary’s County, 81 have given birth in the past 12 months. In Allegany County, only 34 women per 1,000 can say the same. The state average is 56.

The unusually high number in St. Mary’s could mean that the sample of people surveyed in the county was small, Bernstein said, causing an unusually large margin of error of 21. This means that the actual rate of births could be as low as 60 or as high as 102.

“The smaller the population, the larger the margin of error,” Bernstein said. “But this is still a statistically significant difference.”

St. Mary’s County also ranks near the top when it comes to the percentage of households with at least one member under 18, which suggests that St. Mary’s has a younger population distribution than other counties. This would help explain higher fertility rates, Joan Kahn, associate director of the Maryland Population Research Center, said.

Andrew Cherlin, a professor at Johns Hopkins University’s sociology department, said: “Birth rate depends on the number of women of childbearing age. In a county with lots of older women, the birth rate will be lower.”

Despite differing fertility rates, households are roughly the same size across Maryland. Charles County households are largest at 2.8 members, and those in Worcester County are smallest at 2.1.

Average household size, Cherlin said, depends heavily on the number of single households in a county.

“A lot of counties in Maryland have both a substantial number of young adults living alone and also many families,” Cherlin said. “So the families may be having lots of children, but the older children may be living on their own.”

Indeed, the rate of households occupied by married couples also differs widely from one county to the next. While married couples constitute almost two-thirds of Carroll County households, Baltimore City’s rate is only 25 percent. Prince George’s County has the next lowest rate, 39 percent.

Baltimore’s outlier status means mostly one thing: married couples tend not to live in the inner cities, Kahn said.