WOMEN are still a minority among the billionaire set, but the richest female billionaires are wealthier this year than last. The 21 richest women in the world (two women tied at 20th place) have a combined total net worth of $248.6 billion, or an average of $11.84 billion each.

That’s a slight jump up from last year’s 20 richest, whose average net worth was $11.6 billion.The majority of this exclusive set, members of Forbes’ 2012 list of The World’s Billionaires, gained their wealth through inheritance and marriage. But one woman–Chinese journalist-turned-real-estate-developer Wu Yajun–can say her fortune is entirely self-made.Overall, the number of  female billionaires is slowly growing. This year, of the record 1,226 people in the world worth $1 billion or more, 104–just 8.5%–are women. Still, that’s a record number of women on the Forbes Billionaires List. Ten years ago, in 2002, only 36 women were Forbes Billionaires.Of the 21 richest women, seven are American, two Chinese, two German and two Swedes. The richest, for the seventh year in a row, is Christy Walton, who inherited her fortune–now worth $25.3 billion–from husband John Walton after he died in a plane crash. The youngest woman is Chinese heiress Yang Huiyan, 30; the oldest is 92-year-old Anne Cox Chambers, the Cox media empire heiress. Candy heiress Jacqueline Mars, L’Oreal heiress Liliane Bettencourt, and Chambers are the three women who have been on the list every year since 1987, the first year Forbes published its World Billionaires list. Only eight women–five of them Americans–were billionaires then.Brazilian steel heiress Dorothea Steinbruch & her family tied with Spain’s Rosalia Mera–ex-wife of Zara founder Amancio Ortega–for the number 20 spot.Although not in the top 20, of particular note is newly minted Spanx billionaire Sara Blakely, at 41, the world’s youngest self-made female billionaire. Christy Walton & family $25.3 billion U.S., Wal-MartThe world’s richest woman received almost $200 million in Wal-Mart dividends in the past six months. Stock is up 16% over the same time period.Liliane Bettencourt$24 billion France, L’OrealEurope’s richest woman and heir to the L’Oreal fortune suffers from dementia; in 2011, had her fortune placed under the guardianship of her daughter Francoise Bettencourt-Meyers following a very public three-year legal battle. Alice Walton$23.3 billion U.S., Wal-Mart Last November the heiress opened her shining new Crystal Bridges Museum of American Art in the town of Bentonville, Ark.; it includes pieces from her personal collection and the Walton Family Foundation.Georgina Rinehart$18 billion Australia, Mining Australian mining magnate’s fortune doubled to $18 billion thanks to a deal signed in January that will see South Korean steel giant Posco take a 15% stake in her yet-to-be-developed Roy Hill iron ore mine in Western Australia.Iris Fontbona & family$17.8 billion Chile, Mining Iris Fontbona is the widow of Andronico Luksic, who died of cancer in 2005. During a December 2011 telethon, the usually press-averse Fontbona publicly donated $3 million to help Chileans with disabilities. Birgit Rausing & family$14 billion Sweden, Packaging She and her 3 children inherited packaging giant Tetra Laval after her husband’s death in 2000. The $12 billion (sales) company’s breakthrough aseptic packaging technology makes it possible to store beverages like milk and orange juice without refrigeration. Birgit Rausing & family$14 billion Sweden, Packaging She and her 3 children inherited packaging giant Tetra Laval after her husband’s death in 2000. The $12 billion (sales) company’s breakthrough aseptic packaging technology makes it possible to store beverages like milk and orange juice without refrigeration.Forbes.com