Women are just as ambitious as men at the start of their careers but this falters if companies fail to encourage them, according to a study released Wednesday that sought to dispel the myth of a gender ambition gap. A survey by the Boston Consulting Group (BCG) of 200,000 employees, including 141,000 women from 189 countries, found women just as ambitious as men at the outset and companies were at fault for stopping this, not family status or motherhood. Researchers at the global management consultancy found that among employees younger than 30, there was little difference in ambition at first and ambition waned in both sexes over time, but women’s ambition eroded faster than men’s at companies lagging on gender diversity. The ambition gap between women and men ages 30 to 40 was 17 percent at firms that employees felt were least progressive on gender diversity and at these firms only 66 percent of women sought promotion compared with 83 percent of men. But there was almost no ambition gap between women and men ages 30 to 40 at firms where employees felt gender diversity was improving, with 85 percent of women seeking promotion compared with 87 percent of men. “Both genders are equally ambitious and equally rational,” said Matt Krentz, a BCG senior partner and co-author of the report, in a statement. “Ambition is not a fixed trait; it is an attribute that can be nurtured or damaged over time through the daily interactions and opportunities employees experience at work.” The report comes after a World Economic Forum study last year said efforts to close gender gaps in pay and workforce participation slowed so dramatically in the past year that men and women may not reach economic equality for another 170 years. Data from the International Labor Organization shows that the gender wage gap globally is estimated at 23 percent, meaning on average women earn 77 percent of what men earn. Krentz said the BCG study showed that when companies create a positive culture and attitude regarding gender diversity, all women — mothers included — were eager to advance. The BCG proposed a four step plan to close the ambition gap: build gender-diverse leadership teams, make the workplace suitable for both sexes, make and promote structural changes like flexible work, and track progress. “By creating the right culture, companies can foster women’s ambition and tap into the wider pool of talent needed to win in the future,” said Katie Abouzahr, a health care principal at BCG and co-author of the report.