Definition
Lottery Rollover
Also known as Roll Over, Carryover
By Abhinav VasudevanReviewed Editorial policy
In short
A rollover happens when nobody wins the lottery jackpot and it carries into the next draw. Because the accumulated money came from previous ticket sales, a rollover genuinely improves the expected value of a ticket.
When no ticket matches all the drawn numbers, the jackpot rolls into the next draw and grows.
Why it genuinely improves value
This is one of the few places in gambling where the expected return demonstrably rises, and the reason is simple: the rolled-over money was funded by people who already bought tickets and lost.
A normal draw returns perhaps 50% of the current week’s sales. A draw carrying a large rollover returns that 50% plus money contributed previously, so the return on this week’s ticket is higher.
In principle, a rollover large enough relative to ticket sales pushes expected value above 100%.
Why it rarely works in practice
Two effects cancel most of the benefit.
Split risk. Large jackpots generate enormous ticket sales. More tickets means a far higher chance that two or more people match, and the prize is divided equally.
For a 1-in-14-million draw, once sales approach 14 million tickets the probability of multiple winners becomes substantial. Analyses of record American jackpots consistently find that split risk grows faster than the jackpot does, so the largest draws are frequently worse value than moderate rollovers.
Structure and tax. The advertised figure is usually an annuity, and the cash value is 50% to 60% of it. In the US, tax reduces it further.
Caps and must-be-won draws
Most lotteries limit consecutive rollovers, commonly five, after which the jackpot must be won.
If nobody matches all numbers in a must-be-won draw, the jackpot rolls down and is shared among the next prize tier. This produces unusually large payouts for matching five numbers, and it is the best expected value a lottery ever offers, because the entire accumulated pool is guaranteed to be distributed that night.
If you are going to buy lottery tickets at all, must-be-won draws are the rational time to do it.
Common questions
Does a rollover make a lottery ticket better value?
Genuinely yes, because the accumulated money came from previous losing tickets rather than this week's sales. In principle a large enough rollover pushes expected value above 100%.
Why do record jackpots not guarantee good value?
Because huge jackpots attract enormous ticket sales, sharply raising the chance of multiple winners splitting the prize. Analyses of record American jackpots consistently find split risk grows faster than the jackpot does.