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.

In general, the population of Brookline is aging with a 20% increase among people aged 60-84 between 2007-11 and 2017-21, although it also experienced a decrease of 1% among those 85 or older and an 8% increase among youth under 20 during this same time period. Brookline's population is aging less rapidly than the state and nation, both of which experienced growth among people 85 or older (13% and 18% respectively).

Compared to selected localities, Brookline had among the lowest increase in the youth population, trailing Everett (20%), Cambridge (19%) and Arlington (12%).

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.