In a change from last year, the two tops spots belong to Wal-Mart heiresses Christy Walton and Alice Walton.

Christy, widow of the late John Walton, tops the list with $20 billion to her name. When John unfortunately passed away in a plane crash in 2005, she inherited his fortune of $15.7 billion, which has only grown in recent years.

Meanwhile, her sister-in-law, Alice, daughter of Wal-Mart founder Sam Walton, sits just behind her in second place with a net worth of $19.5 billion. Alice, no stranger to controversy, in 1989 was involved in a car accident that killed a 50-year-old lady in Arkansas. Although it was her speeding that led to the incident, no charges were filed in connection with case. Then, in 1996, she was arrested for driving under the influence of alcohol.

In describing how the Waltons have accumulated such massive wealth, Forbes tipped its hat to Wal-Mart, crediting the world's largest retailer for powering through the global recession. Wal-Mart, which has more than 7,900 stores and two million employees, last year recorded $400 billion in annual sales.