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.

The population of the 3-county MetroWest region has been aging. The number of people between the ages of 60 and 84 increased 43% between 2000 and 2016-20. The population 85 and older grew 39% during the same period. By comparison, the population 40 to 59 grew by 9%, the population 20 to 39 grew 1%, and the population under 20 decreased by 2%. Since 2000, people between 20 and 39 overtook those 40 to 59 as the largest single age group in the region (862,000 residents, compared to 855,000).

One of the most dramatic age shifts in a particular locality has been in Lincoln, where those aged 20 to 39 and those under 20 declined by 46% and 20%, respectively. Bedford is one of the few localities to have growth in both the under 20 and the 20 to 39 population categories (19% and 8%, respectively), along with Waltham (3% and 4%, respectively). In addition, Wellesley had growth of more than 20% in the under 20 category.

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.