Women hold only 3 percent of seats on the boards of directors at Japan's largest companies, the lowest ratio of 20 major economies, a new study shows.

Norway was the most female-friendly, with 36 percent of seats held by women, followed by Finland and France with about 30 percent each, according to the study by Catalyst Inc., a New York-based organization that advocates for greater female representation in the workplace.

The U.S. and Canada had about 20 percent while Portugal, India, and Ireland each had 10 percent or less.

"I'm not madly in love with where we are, but I'm comfortable with where we're going," said Alex Johnston, Catalyst Canada's executive director. "What's giving me enthusiasm is what's going on on the ground. People are saying there's a momentum shift."

Companies are striving to boost females in executive and leadership roles at the urging of lawmakers and organizations such as the U.K.-based 30 Percent Club. In Canada, securities regulators implemented a rule last year requiring companies to disclose policies and targets for female recruitment and promotion in annual reports.

The 30 Percent Coalition, whose members include Pacific Investment Management Co. and Goldman Sachs Group Inc., is the U.S. equivalent and aims for about one-third female representation across U.S. public company boards by the end of this year.

The research, done in partnership with Data Morphosis Group, analyzed each country's largest stock market index based on October 2014 data.