Forbes released its second-annual ranking of America’s richest families this week, with the Waltons (founders of Wal-Mart) at the top the list for the second year in a row. Three children of Wal-Mart's original founder, Sam Walton, a daughter-in-law, and two grandchildren own 54% of the shares, and are collectively worth a whopping $149 billion. Forbes capped the list at 200 people — 193 dynasties — worth a total of $1.3 trillion. The top 20 richest families have made their money in a wide variety of ways — everything from soup to magazines. So what qualities do families need to have to make this list (besides $1.2 billion)? "A successful dynasty requires heirs to think like their ancestors," Forbes editor Abe Brown says. "The people who started these great legacies are driven individuals who spent a long time planning their business empire — and planning how they’d leave it to the next generation." Unfortunately, most of these companies were founded by patriarchs. Only one women made the top 20: Estée Lauder, American businesswoman and beauty magnate, whose family's wealth is reported to be $16.5 billion. Brown attributes the lack of female-fronted companies to time: "Nearly all these fortunes were created at a time when women simply didn’t start businesses — we’re talking the late 19th century and early 20th." Not to worry, Brown believes this gender imbalance will improve in the future: "If you look at this list again in 50 years, you’ll see more matriarchs." Maybe the children of Birchbox or LearnVest's founders will make the cut one day?