New Jersey’s booming immigrant communities not only keep the state’s population growing, but also make it one of the most diverse in the country.

At least 290 towns in the state have seen an improvement in diversity over the past decade, an analysis of census data shows.

If we went back a hundred years, New Jersey was still diverse — with large immigrant populations — but they were segregated into neighborhoods.

Back then, you could attribute that to the proximity to Ellis Island. Now, the presence of major international airports such as Newark and JFK and the state’s proximity to New York City have kept up the flow of people, said James Hughes, dean emeritus of the Bloustein School of Planning and Public Policy at Rutgers University.

And experts say large concentrations of immigrants in a community can act as a force multiplier, drawing newer immigrants to a town or city. New Jersey politicians’ efforts to attract people from different backgrounds is another factor to consider, Hughes said.

“Most of the politicians realize that the new population coming in is important for their political future. So they’re savvy enough to be very sensitive for the most part to the needs of new arrivals,” he said.

To look at what diversity really meant, we calculated something called the diversity index. Most measures of diversity look at the percentage of population of minority racial or ethnic groups by themselves.

The diversity index asks a different question: How well-balanced are all the racial and ethnic groups in this town?

More specifically, it measures the chance of picking two random people out of a town’s population, and having them be from different ethnic groups. The numbers are between 0 and 1. Zero indicates no diversity — everyone is the same. One, or 100%, indicates perfect diversity — all individuals are different. The state’s diversity index of 0.66, or 66%, in 2018 ticked up from 2010′s 0.63 or 63%.

The most diverse towns list for 2018 was not very different from what we’ve been seeing at for the past few years: Paterson, Camden, Elizabeth, Jersey City and Atlantic City were at the top. Eighty-one towns had diversity indexes higher than the state’s. They were mostly concentrated in Bergen, Middlesex and Hudson counties.

Some towns stood out because of the gains they made in diversifying their populations. North Hanover in Burlington County, for example, had a diversity index of 26% in 2010. In 2018, that rose to 62%, the largest change in any New Jersey town.

This overall increase was fueled by a slight uptick in the Black population and some decrease in the white population, although the latter still remains the largest group. This made the different groups more balanced, which is what the diversity index indicates.

About the data: NJ Advance Media compared the 2018 American Community Survey snapshot with the 2010 ACS snapshot to calculate the diversity index, using the equation created in 1991 by Phil Meyer at the University of North Carolina and Shawn McIntosh of USA Today. Princeton was left out of the analysis as the present-day town used to be two different towns in 2010. Towns with population less than 5,000 were eliminated from the analysis as they tend to have a higher margin of error and can skew the results.

Disha Raychaudhuri may be reached at disha@njadvancemedia.com. Follow her on Twitter @Disha_RC.