The number of billionaires around the world is growing, rising by 15% to 2,754 people in 2017 from the previous year, according to data by market research firm Wealth-X.

Out of that total number of billionaires, there are 321 women—a rise of 18% from last year, outpacing the growth of 14.5% in the male billionaire population. However, when you look at the reasons for the source of their wealth, inheritance takes up a far greater proportion than men’s.

Wealth-X notes that while there is a stark contrast between the genders when it comes to the origin of their wealth, within the female population, there has been a steady rise in the share of those whose net worth can be attributed both to inheritance and to self-made means. The firm says the data are “implying a greater degree of risk-taking entrepreneurialism.”

For example, Russian-born businesswoman Margarita Louis-Dreyfus (paywall) is one of the richest women in the world with a net worth of $5.2 billion, according to Forbes. On a flight in 1988, she met her husband Robert Louis-Dreyfus, the former CEO of UK advertising firm Saatchi & Saatchi and part of the family behind the Louis Dreyfus Company, a commodities group with businesses in agriculture, food processing, international shipping, and finance. However, when he died of leukemia in 2009, she became the majority owner and chairman of the Louis Dreyfus Company and continues to work there to this day.

Among the world’s most well-known self-made female billionaires is Italy’s Giuliana Benetton, who has a net worth of $3.6 billion, according to Forbes. After her father’s death, she knitted sweaters that her older brother sold at a shop to help pay the bills. In 1965, she and her three brothers founded clothing giant Benetton.