A Lottery Loophole (Sorry, Now Closed) in Massachusetts

In the Boston Globe, Andrea Estes and Scott Allen write about how people have been taking advantage of a statistical quirk in the rules of an obscure Massachusetts Lottery game called Cash WinFall. A Michigan couple in their 70s, Marjorie and Gerald Selbee, spent three days buying more than $600,000 in Cash WinFall tickets from two convenience stores in Sunderland, Mass. Their timing was purposeful:

For a few days about every three months, Cash WinFall may be the most reliably lucrative lottery game in the country. Because of a quirk in the rules, when the jackpot reaches roughly $2 million and no one wins, payoffs for smaller prizes swell dramatically, which statisticians say practically assures a profit to anyone who buys at least $100,000 worth of tickets. During these brief periods - “rolldown weeks’’ in gambling parlance - a tiny group of savvy bettors, among them highly trained computer scientists from MIT and Northeastern University, virtually take over the game. Just three groups, including the Selbees, claimed 1,105 of the 1,605 winning Cash WinFall tickets statewide after the rolldown week in May, according to lottery records. They also appear to have purchased about half the tickets, based on reports from the stores that the top gamblers frequent most.