Buying lottery tickets may seem like an irrational waste of money. But people do it anyway—often spending $50 or $100 a week. And some do it consistently for years, defying the expectations you might have about them: that they’re irrational and duped by their slim chances of winning.

Lottery proceeds often help support areas of public budgets in need of funding, such as education. It’s a popular way to raise funds, and its origin dates back centuries. However, there are a few things you should keep in mind when purchasing your tickets.

It’s not uncommon for people to choose numbers that are personal to them, such as birthdays or other lucky combinations, but this is a bad idea because the number pattern may actually be more likely to repeat in subsequent drawings. Instead, Clotfelter suggests choosing a random group of numbers or letting the computer pick them for you.

A lottery prize is determined by the total amount raised, minus expenses. The prize value is generally predetermined, although a promoter may decide to raise the total if there are enough participants and it’s deemed financially feasible.

Lottery advertising often depicts past winners or dreamers of wealth, tapping into the aspirations of audiences. And it’s not just about the potential winnings: Lottery marketers also emphasize the simplicity of playing, which is important for attracting new gamblers.