The "No Ceilings" report is a review of progress made by women since the 1995 Beijing conference laid out a platform of action for achieving gender equality.
It was at that gathering that then first lady Hillary Clinton declared: "Let it be that human rights are women's rights, and women's rights are human rights, once and for all."
But 20 years on, women are still "very much a minority" when it comes to holding political office, representing fewer than 30 percent of the world's lawmakers, the report said.
Women hold finance or budget cabinet posts in just 24 of 189 countries studied for the report.
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UN Secretary-General Ban Ki-moon has noted that five countries still have all-male parliaments, and eight countries do not have a single woman in cabinet.
The report was released at the start of a 12-day UN conference on women that will focus on women's political power and their influence in economic decision-making.
Women are increasingly taking their place on board seats, with their share ranging from eight percent in Portugal to 36 percent in Norway, but this falls short of parity, the study said.
Clinton, seen as the likely Democratic presidential frontrunner, will attend the UN conference tomorrow to address the "unfinished business" of the Beijing gathering, aides said.
Despite shortcomings in politics and economic representation, women have made headway in health and education, with women now outnumbering men in universities.