Population measures provide insight on the changing size and face of communities, and an area's needs and assets. For example, areas with large or growing populations of seniors or children may face challenges in providing needed services and generating enough tax revenue to support those services.

TThe population of Lancaster County has been aging. The number of people between the ages of 60 and 84 increased 31% and the population aged 85 and older grew 21% between 2007-11 and 2017-21. By comparison, the population aged 40 to 59 declined by 6%, and there was only a slight increase of 9% among people 20 to 39. There has been no change in population among those under 20. Since 2007-11, people under age 20 have been the largest single age group in Lancaster County, with almost 145,000 people, followed by those between the ages of 20 and 39 and people between 40 and 59, with approximately 138,000 and 133,000 people in each group respectively.

One of the most dramatic age shifts in a particular locality has been in Chester County, where those aged 60 to 84 increased by 41% between 2007-11 and 2017-21. Lebanon and Cumberland counties had the largest growth in the under-20 category both at 7%. The City of Lancaster is one of the few localities to experience declines, specifically among those 85 or older, which declined 35%, and among those under 20, which declined by 15%.

The multi-year figures are from the Census Bureau's American Community Survey. The bureau combined multiple years of responses to the survey to provide estimates for smaller geographic areas and increase the precision of its estimates. The survey provides data on characteristics of the population that used to be collected only during the decennial census. Data for this indicator are expected to be released in the fourth quarter.