Maine’s population is expected to grow by less than half of one percent a year before it peaks in 2020, and begins to shrink.

If you think that’s good news, think again.

Population decline goes hand in hand with economic ruin. Where there are not enough workers, investment dries up, jobs vanish and fewer people are left paying the bills.

That’s why the state economist and others identify migration as essential to the survival of the oldest state in the country, where nothing is growing faster than the percentage of people who are too old to have babies. The only way to grow is through migration of people from other states and from abroad.

A new report by the city of Portland and the Portland Regional Chamber of Commerce offers a glimpse of how people born in other countries – the ultimate “people from away” – can contribute to a local economy. The experience in southern Maine shows that an influx of immigrants is something to welcome, not fear.

The study looked at a five-year period beginning in 2011. Greater Portland still has a much lower foreign-born population than the country as a whole, but it is growing locally at a much faster rate than the region’s population as a whole, and the people who come here from other countries are playing a disproportionate role in the economy.

Immigrants make up only 4.6 percent of the population (as opposed to nearly 15 percent nationally). But immigrants account for over 5 percent of the working-age population in Greater Portland and 6 percent of the workers in science and technology jobs.

A higher percentage of immigrants hold college degrees than the general population and they have a higher rate of starting businesses. And according to the report, they added $1.6 billion to the local economy.

There is a lot that this report did not measure. There are costs to integrating a foreign-born population, such as providing language training in some cases or assisting with food and housing for asylum seekers who are legally prevented from working.

But it’s a mistake for Mainers to focus only on the costs and not the benefits.

Maine’s future will be bleak if we don’t grow the workforce. Greater Portland is showing how to do it.