If you’re lucky enough to win a lottery jackpot, you have some big decisions to make. First, you have to choose whether you want a lump sum or an annuity. A lump sum would come in one big payment, while an annuity is a series of annual payments that increase every year. The decision depends on your age, financial goals, and tax situation. But whatever you decide, it’s crucial to plan ahead.

Lottery organizers have been gradually making jackpots bigger and bigger for decades by changing the formulas used to calculate them, says math professor Tim Chartier. The resulting increase in jackpots attracts new players and fuels a self-fulfilling cycle: as ticket sales climb, the odds of winning the prize rise, too.

Some people who wouldn’t otherwise play the lottery will buy a ticket when the jackpot hits $1 billion. But what really drives lottery ticket sales is the size of the prize, Matheson says. “It’s this inextricable human impulse to dream big,” he says.

Ultimately, if the prize grows too large, there’s a good chance that someone will win it on a regular basis, and that can drive ticket sales down. That’s why some states have also been increasing or decreasing the number of balls in the game.

After you’ve made your choice, you’ll have to work out the details — including federal and state tax withholdings, which will be roughly 24 percent and 4.99 percent, respectively. Then you’ll need to find a lawyer you trust, and a financial advisor you can rely on. Finally, you’ll need to figure out how to spend or invest the money wisely.