Few people, from politicians to commenters on Facebook, expressed surprise when The Baltimore Sun reported Thursday that the city’s population has continued on a downward trajectory.
Some did wonder, though, whether the minuscule number of people lost was worth reporting and how the U.S. Census Bureau arrived at its estimates.
Baltimore’s loss was teensy. Only 0.2 percent of Charm City’s population — 1,500 people — departed in the 15-month period following the April 2010 Census, according to the Census Bureau’s first city population estimates of the decade.
That loss may seem insignificant, stacked atop six decades of major population decline. In the first 10 years of this century, the city lost 3,000 people on average per year.
But when compared to population trends in other large U.S. cities, Baltimore stands in stark contrast.
Urban centers across the country are growing. On average, cities with populations of 100,000 or more people grew 1.3 percent between April 2010 and July 2011. Smaller cities are thriving, too; no place with a population of 50,000 or more people dropped below that level during that stretch.
Of the 715 incorporated places in the U.S. with populations over 50,000, just over 50 lost residents. Most of those are located in the Northeast or Midwest and were once thriving industrial towns.
Only Cleveland and Detroit lost more people, in terms of raw numbers, than Baltimore. Cleveland shed about 3,000 people, Detroit over 7,000. Other major cities that lost population include Toledo and St. Louis.
The Census Bureau releases updated population estimates every year. They’re extrapolated from the most recent census numbers, said Rodger Johnson, a Census Bureau demographer.
The estimate for Baltimore, and any other place that is equivalent to a county, is calculated simply by taking the base population count — the number of people living in Baltimore on April 1, 2010 — then adding births, subtracting deaths and taking into account domestic and international migration expectations, Johnson said.
The estimates for places like Cleveland and Detroit — and most other U.S. cities — are calculated differently, he said, because typically cities are a subset of a county, and Baltimore is not.
After the population estimate for a county is complete, the Census Bureau uses an estimate of the change in the number of housing units in a place to allocate a county’s population gain or loss among its cities, boroughs, villages and other incorporated places, Johnson said.
“Baltimore may be at a disadvantage because it is not within a county,” said Andrew Ratner, a spokesman for the Maryland Planning Department.
Perhaps some cities are being buoyed by growth in their county’s suburbs, he suggested.
So can the population estimate of a city that is a county equivalent be compared to the estimate of a city that is subsumed by a county?
“In relative terms, you certainly can compare them,” said Johnson. “The estimates are made slightly differently but they still represent a pretty fair estimate of the population dynamics that are going on in that community.”