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Monday, January 28, 2019  01:00 PM  (16)

Ongoing demographic change in the City of Pittsburgh

Demographic change is not new for the city of Pittsburgh, but there is evidence some longstanding trends have reversed in the most recent years. The graphics below combines data on population by race from the most recent five decennial censuses (1970, 1980, 1990, 2000 and 2010) along with population estimates compiled from the American Community Survey (ACS), which pubishes more recent information on the demographic profile of City of Pittsburgh residents.  

What stands out is an acceleration in the rate of decline in the city’s black population, while the decline in the city’s white population appears to have abated.  These trends contrast with past patterns where the city’s white population consistently declined faster than the black population through the latter half of the 20^th century.   

Note that the graphic combines data from different Census Bureau programs which are not directly comparable with each other, or over time.  Each decennial census attempts to be a complete enumeration of the nation's population in April of the first month of each decade. The ACS is an ongoing sample-based program that collects data through the year. ACS-based population characteristics are imputed from the survey results collected over a one-year period, and for smaller areas, data is only made available for aggregated 5-year periods. Sampling, and other factors introduce error into ACS estimates that is not present in decennial census data on population by race. 

The ACS data presented here are from the 5-year estimates, which have much smaller measurement errors than 1-year ACS-based estimates available for the city. The graphs show the rate of population change between decennial censuses, and between subsequent non-overlapping 5-year periods for the ACS data. For each period, the compound average annual rate of change in the population is calculated to aide comparison of the different periods. The change between two subsequent 5-year ACS periods is presumed to reflect change over a five year period. 

Also, the Census Bureau’s methodology for collecting population data by race has changed significantly in recent decades. Between 1970 and 1990, each decennial census categorized all individuals in a single race category.  Starting with the 2000 decennial census, and for all ACS data, census respondents could identify themselves among multiple race categories.  Here, the changes between decennial censuses in 1970, 1980 and 1990 reflect the single-race data collected in those years.  For change between the 2000 and 2010 decennial censuses, and for the ACS periods shown here, the data reflects the change in black-alone and white-alone populations resident within the city of Pittsburgh. 

For change between 1990 and 2000, two rates of change are computed for each race.  The single-race population counts in 1990 are compared to 2000 data reflecting either the black-alone or white alone population in each graph. The alternative rate of change compares the same single-race 1990 population counts to either the count of the black population, either black alone or in combination with any other race, or the white population alone or in combination with any other race.

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