According to the new county-level population estimates released by the U.S. Census Bureau, the greatest numerical increases in Massachusetts counties from July 1, 2023 to July 1, 2024 were seen in Middlesex County at 24,024 net persons gained; Suffolk at 11,466; and Worcester at 8,435. Norfolk County was the fourth fastest grower this year with 8,375 persons added net. In terms of percentage change, the largest net gains were in Suffolk County and Middlesex County both with 1.5% increases from 2023 to 2024. These large population increases are attributed primarily to increased immigration in the V2024 population estimates series, which is most pronounced in the state’s five largest counties: Middlesex, Worcester, Essex, Suffolk, and Norfolk. The increased immigration in MA is attributed to a surge in humanitarian migrants, the post-pandemic rebound in U.S. immigration, and a change in the U.S. Census Bureau’s immigration estimates methodology.

The slowest growing counties in the 2023-2024 period by population count were Hampshire, with an estimated 287-person net loss; Barnstable, with a 189-person net loss; and Berkshire, with an estimated loss of 137 persons. The largest percentage decreases were in Hampshire (-0.2%), Berkshire (-0.1%) and Barnstable Counties (-0.1%). Population loss in these areas during the 2023-2024 period can be attributed to a number of factors, including a reversion to pre-pandemic trends, as seen in Berkshire and Barnstable County. During the pandemic, many people moved to seasonal homes in the Berkshires or Cape and Islands, but the extent to which these moves are permanent is yet to be discovered. Domestic migration into these areas remained robust in 2021, but we now see a reversal of that trend in Berkshire and Barnstable Counties in the years 2022 through 2024.

County-level estimates are produced by the U.S. Census Bureau using the latest data available for the various components of change, which include births and deaths, domestic migration (within the United States) and international migration, and the group quarters population for each county. During the period of July 1, 2023 to July 1, 2024, half of the 14 counties in Massachusetts had a positive net natural increase in which the number of births was greater than the number of deaths. These counties were Middlesex (+4,525), Suffolk (+3,541), Essex (+1,270), Norfolk (+1,086), Worcester (+738), Nantucket (+62), and Dukes (+1). Counties with the largest negative net natural increase were Barnstable (-1,728), Berkshire (-868), Bristol (-818), and Hampshire (-529).

The migration figures within the components of change estimates show the majority of Massachusetts counties—9 out of 14—have negative domestic migration, meaning populations have moved from these counties to other counties within the U.S. These negative domestic counties include Suffolk, Middlesex, Essex, Worcester, Norfolk, Hampshire, Hampden, Nantucket, and Dukes In all nine of these  counties, however, the negative domestic migration is offset completely by international immigration for a positive total net migration. A rebound in immigration in Massachusetts since the pandemic years and a revision to the Census Bureau’s immigration methodology this year both factor into significant immigration levels in Massachusetts counties in 2024, particularly in the more populous counties of Eastern MA. At the state-level, international migration estimates reached a record high since at least 2000 with the arrival of 90,217 residents–-outweighing domestic migration loss across the state and resulting in a positive total migration figure of 62,737.

For more information about the Vintage 2024 county-level population estimates, download the full UMDI report and prepared workbook below or visit the U.S. Census Bureau’s Population and Housing Unit Estimates website.

Estimates for Massachusetts follow the national trend, showing a population that is growing older and more racially and ethnically diverse. Even though Massachusetts is less diverse than the U.S. average—with a combined ethnic and racial minorities population of just 31.2% compared to 41.6% in the U.S. —the minority population in Massachusetts has been increasing at a faster rate than the U.S. average.  From 2010 to 2023, the minority population in the state increased by 8.1 percentage points—from 23.1% to 31.2%—compared to a 5.6 percentage point increase in the U.S. overall. All Massachusetts counties have experienced increasing diversity since 2010 by varying degrees around the state.

The Massachusetts counties with the greatest percentage of combined ethnic and racial minorities populations in 2023 were Suffolk (55.0%), Hampden (40.3%), and Essex (33.8%). The counties with the lowest percentage were Franklin (11.3%), Barnstable (11.5%), and Berkshire (13.7%).   

Massachusetts has an estimated median age of 40.3 years in 2023. As of 2023, 10 out of 14 Massachusetts counties—over two-thirds—have a median age 40 or over. The counties with the highest median age are Barnstable (56.1 years), Dukes (50.5 years), and Berkshire (48.2 years), while the counties with the youngest median ages are Suffolk (34.4 years), Hampshire (37.7 years), and Middlesex (39.2 years). At the other end of the age-spectrum, counties with the highest percentage of children under 18 years of age include Essex (20.6%), Hampden (20.6%), Plymouth (20.4%), and Worcester (20.4%).

For more details on selected Massachusetts characteristics data and trends, please refer to the Summary of U.S. Census Bureau’s 2023 County Characteristics Estimates for Massachusetts Counties and the related Appendix in the Resources and Downloads section below.  You may also view the complete datasets by visiting the U.S. Census Bureau’s Estimates page.