The lottery is a popular form of gambling, and it’s also one that has some serious pitfalls. As HuffPost’s Highline has documented, a Michigan couple made $27 million over nine years playing the state’s lotteries, thanks to a strategy that involved bulk-buying thousands of tickets each time, ensuring that odds were in their favor, and basically turning playing the lottery into a full-time job. This sort of behavior, coupled with the largely mythological belief that everyone can win if they buy enough tickets, obscures the fact that lotteries aren’t just games—they’re majorly regressive.

The idea of lotteries dates back to ancient times. The Old Testament mentions giving land and slaves through them, and Roman emperors gave away goods like dinnerware to guests at their parties. These were essentially private lottery games, but public lotteries began to appear in the Low Countries during the 15th century. These helped raise money for town walls and for poor people.

Today, 44 states and the District of Columbia run lotteries. Six don’t—Alabama, Alaska, Hawaii, Mississippi, Utah, and Nevada—for reasons that range from religious concerns to resentment of the state government getting too much of the revenue from the lottery. Even so, the vast majority of Americans play the lottery. And there’s an interesting pattern to how that happens. As we’ll see, the odds of winning a lotto vary considerably, depending on how you select your numbers. This is because combinations of numbers can be organized into combinatorial groups based on their composition. Different combinatorial groups exhibit varying success-to-failure ratios, and we’ll see that selecting certain types of numbers can increase your chances of winning.