Foreign-born Americans and their descendants have historically been a main driver of population growth, and that role will only increase in the future. According to the Pew Research Center, new immigrants and their children and grandchildren accounted for 55% of the U.S. population increase from 193 million in 1965 to 324 million in 2015. Pew projects the population will grow to 441 million in 2065 and that 88% of the increase is linked to future immigrants and their descendants. This measure also is a reflection of the composition of a community, which can offer insight into its levels of diversity.

In 2016-20, 18% of the population in MetroWest and 17% in Massachusetts was foreign-born, slightly higher than the national rate of 14%. The percentage in both MetroWest and the state increased by 5 percentage points from 2000, while the nation increased by 3 points.

Within the MetroWest region, Lexington has the highest percentage of foreign-born residents, 29%, comparable to Boston. It is closely followed by Framingham and Westborough both at 28%, Acton at 27%, and Marlborough at 24%. Westborough had the greatest increase in rate since 2000, increasing 14 percentage points, followed by Acton, Lexington and Bedford, all at 13 points. Framingham had the largest absolute number of foreign-born residents, at 20,700, followed by Waltham at 16,700.

The multiyear figures are from the Census Bureau's American Community Survey. The bureau combined 5 years of responses to the survey to provide estimates for smaller geographic areas and increase the precision of its estimates. However, because the information came from a survey, the samples responding to the survey were not always large enough to produce reliable results, especially in small geographic areas. CGR has noted on data tables the estimates with relatively large margins of error. Estimates with three asterisks have the largest margins, plus or minus 50% or more of the estimate. Two asterisks mean plus or minus 35%-50%, and one asterisk means plus or minus 20%-35%. For all estimates, the confidence level is 90%, meaning there is 90% probability the true value (if the whole population were surveyed) would be within the margin of error (or confidence interval). The survey provides data on characteristics of the population that used to be collected only during the decennial census. Data for this indicator are released annually in December.