Women are outpacing men in reaching billionaire status, says UBS and PricewaterhouseCoopers.

The number of women who can claim to have at least a billion dollars has grown 6.6 times in 20 years compared to a 5.2 times growth for men, according to a firm released by the companies.

In the last 20 years, the number of women billionaires has grown from 22 to 145. Asia women have led the way in the growth, from only three 10 years ago to 25, according to the study. This compares to a growth from 21 to 57 over 10 years in Europe and 37 to 63 in the U.S. Asian women billionaires tend to be younger, while Americans and Europeans are older and often represent multigenerational wealth.

The UBS/PwC study says three personality traits have been shown to be essential to entrepreneurial success for both genders – smart risk taking, obsessive business focus and dogged determination. Billionaires have grown their average assets from $2.9 billion to $11 billion over 20 years, outperforming both equity markets and global GDP. Total billionaire wealth now stands at 44.7 trillion.

Two-thirds of billionaires are over 60 years’ of age and face critical wealth transfer decisions, says UBS/PwC. More than three-quarters of the billionaires have two or more children. To avoid wealth dilution as the next generation and subsequent generations grow larger, a clear wealth preservation strategy is required to ensure the creation of long-term lasting legacies, the study says.