This article appeared in June, but we resurfaced it because the German parliament on Friday, March 6, passed a law that mandates giving 30 percent of supervisory board seats in some of Europe’s biggest companies to women starting next year.

One of the most perplexing questions about women in business is how to increase their numbers in the upper ranks, where their progress to the top has stalled.

An increasingly popular idea in Europe is affirmative action for executives — requiring companies to include a certain percentage of women in management, particularly on their boards. Improvement at the top, the thinking goes, is likely to filter down at companies, improving the pay and representation of women at lower levels.

Norway passed a law in 2003 requiring that women make up 40 percent of the boards of public companies. Many countries, including Spain, Iceland, Italy, Finland and France, followed suit. Advocates have proposed quotas in the United States, though companies here tend to bristle at the idea that the government could tell them whom to hire. In April, two dozen American companies, including Bloomberg, DuPont and Deloitte, opened the United States branch of the 30% Club, which was started in Britain as a group of companies that aims to voluntarily appoint boards in which 30 percent are women.