This just in from the US Census:
New Census Bureau Population Estimates Pinpoint Fastest-Growing Counties in Massachusetts
March 24, 2016 ─ The U.S. Census Bureau reported today on where the heaviest population growth in Massachusetts was concentrated last year.
The fastest-growing county in Massachusetts between July 1, 2014, and July 1, 2015, was Suffolk county, whose population rose 1.1 percent over the period. Suffolk county was followed by Nantucket (1 percent), Middlesex (0.8 percent), Essex (0.7 percent) and Plymouth (0.7 percent).
With respect to numerical growth, Middlesex county added 12,616 people over the period, more than any other county in the state. It was followed by Suffolk, which grew by 8,312 people, Essex (5,557), Worcester (3,991) and Plymouth (3,343).
Middlesex is the most populous county in Massachusetts, with 1,585,139 residents, followed by Worcester and Suffolk.
This information is based on annual population estimates for each of the nation’s counties, county equivalents, metropolitan statistical areas, and micropolitan statistical areas since the 2010 Census and up to July 1, 2015. Internet tables are available showing rankings and components of population change (births, deaths, migration).