Though there are still 8 times as many super-rich men, the number of female billionaires has multiplied by 7 over the last 20 years from 22 to 145.

Most female billionaires are based in the United States and Europe (about 80%), and a vast majority of these women (81% in the U.S. and 93% in Europe) inherited their fortune. However, more than half of the 25 Asian female billionaires are self-made, according to a report by UBS and PwC.

Just one decade ago, there were only 3 female billionaires in Asia. Today's female Asian billionaires tend to be younger than their Western counterparts, too, with an average age of 53 compared to 59 in the U.S. and 63 in Europe.

Many Asian women on the list of billionaires built their wealth after working hard to pay for Western education, then returning home to make their fortunes. One billionaire in the study said she worked in a factory for several years while saving up to study abroad and earn a degree.

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