The pay gap between men and women in their 20s has halved in a generation to 5 percent but will widen as the same adults grow older, according to analysis by a British think-tank, reported by Reuters.

The analysis of data from the Office for National Statistics by the Resolution Foundation found the gender pay gap has closed for every generation of women since those born between 1911 and 1925.

"Young women today face relatively little disadvantage in terms of their pay packets compared to what their parents' and grandparents' generation faced," said Laura Gardiner, senior policy analyst at the nonpartisan foundation.

According to the study, the gender pay gap has fallen from an average of 16 percent for baby boomers born between 1946 and 1965, to 9 percent for Generation X, born between 1966 and 1980, and to 5 percent for millennials, or those born between 1981 and 2000.

However, the pay gap begins to widen as women begin to enter their 30s and early 40s when they begin to have children and begin to take time off work, after which it continues for decades, the study said.