Ukraine needs its women refugees to come home, and soon.

Almost a year and a half into Russian President Vladimir Putin’s faltering invasion, the cost of resistance for Russia’s neighbor has been devastating. Unless Ukraine’s six million-plus refugees return, some of that damage will be permanent.

Most men age 18 to 60 aren’t allowed to leave the country, which explains why 68% of Ukrainian refugees are women, with an even greater gender disparity among adults. Failure to persuade any of the 2.8 million working-age women to return would cost Ukraine 10% of its annual prewar gross domestic product, according to Alexander Isakov of Bloomberg Economics.