The U.S. economy could be $1.6 trillion larger than it is today if women entered and stayed in the workforce at the same pace as Norway, according to an analysis by S&P Global economists.

S&P Global believes that a dual-pronged effort to encourage women to enter the workforce and stay there, particularly in professions traditionally dominated by men, would present a substantial opportunity for growth of the world’s principal economy, with the potential to add 5%-10% to nominal GDP in just a few decades.

In 1990, the prime-age U.S. female labor participation rate was closer to the top of 22 advanced Organization for Economic Cooperation and Development economies. As of 2016, it is down to No. 20, near last place in terms of optimizing what is considered to be an economy’s most valuable resource — labor.

The labor-force participation rate — now near a 40-year low — has increasingly become a drag on growth since the turn of the millennium. And lost labor-force participation means lost economic activity, according to S&P.

Because of this prolonged drag on growth, S&P Global U.S. Economics recently lowered its estimate for the potential long-term average annual economic expansion to just 1.8% — one percentage point lower than its 2.75% estimate of 15 years ago.

The labor force participation rate for women of prime working age in the U.S. in 1990 reached 74%, one of the highest rates in the world. Since then, that rate has stayed roughly stable while increasing steadily elsewhere, pushing the U.S. down to 20th place among 22 advanced OECD economies by 2016.

Growth in the labor force participation rate of Norwegian women, for example, has significantly outpaced that among American women for the last few decades.

U.S. women’s labor force participation rate peaked at 60.3% in March 2000, increasing by an annualized 1.3% from 1972, when it was 43.9%, according to the Bureau of Labor Statistics.

Meanwhile, the rate among Norwegian women reached 68.9% in 2000 (and peaked at 70.7% in 2008), up from 44.8% in 1972. That’s an annualized pace of 1.9%, about 45% faster than in the U.S.

“If the growth in the women’s [labor force participation rate] in the U.S. had matched that of Norway from 1970-2016 (with all other factors constant), the U.S. economy would be approximately $1.6 trillion bigger than it is today,” the report states. “That’s an extra $5,000 or so for every man, woman, and child in the country — a lack of economic growth that affects everyone indiscriminate of gender.”

In terms of annual economic expansion, the S&P finds that real GDP growth would have averaged 3.1%, rather than 2.9%, and the compounded expansion for the 46-year period would have been 311% rather than the (still impressive) 278%.

— Check out ‘Fearless Girl’ Was Never a ‘Statement of Accomplishment’: State Street on ThinkAdvisor.