LotteryJackpots don't grow because a lottery commission decides to make them bigger — they grow through a fairly mechanical process tied directly to ticket sales and rollovers. Understanding the mechanism explains a few things that otherwise seem arbitrary: why some droughts push a jackpot past a billion dollars and others stall out at $40 million, and why the advertised number keeps climbing right up until the moment someone wins.
The Basic Mechanism: Rollovers
Each drawing, a portion of every ticket sold goes into that game's jackpot prize pool. If nobody matches every number, the jackpot "rolls over" — it carries forward and combines with the contributions from the next drawing's ticket sales. This repeats drawing after drawing until someone finally matches the full combination, at which point the entire accumulated pool is paid out and the jackpot resets to its starting amount for the next cycle.
This is why a jackpot's size is really a record of how many consecutive drawings have gone by without a winner, combined with how many tickets were sold during that stretch — not a number anyone sets in advance.
The Self-Reinforcing Loop
Here's the part that produces those eye-popping headline jackpots: bigger advertised jackpots draw more media attention, which draws more casual/occasional players who don't normally play, which increases ticket sales, which increases the next jackpot even faster if it also isn't won. A moderate jackpot might grow by tens of millions per drawing; once a jackpot crosses a few hundred million and starts making national news, sales spike and growth can accelerate substantially per drawing. This feedback loop is a large part of why the very largest jackpots in history all came from unusually long winless streaks rather than gradually predictable growth.
Why Ticket Price Changes Growth Rate
Mega Millions costs $5 per play versus Powerball's $2, which means a comparable number of tickets sold contributes more total revenue — and therefore more jackpot growth per drawing — for Mega Millions than for Powerball, all else equal. This is one of several factors (along with each game's specific odds and draw frequency) behind why the very largest jackpots in U.S. history have come from both games at different times, rather than consistently favoring one. We compare the two games more broadly in Powerball vs. Mega Millions: Which Has Better Odds and Bigger Payouts?
Why the Cash Value Grows Differently Than the Annuity Number
The advertised jackpot is the annuity figure — the total of 30 payments over 29 years. The cash value (what's actually available as a lump sum today) is based on the actual money sitting in the prize pool, which is smaller because the annuity figure assumes that money is invested and grows over three decades. This means the cash value and the annuity value don't grow at exactly the same rate as ticket sales increase; the gap between them is also sensitive to prevailing interest rates, since higher rates make the invested-annuity math produce a bigger theoretical annuity number relative to the same amount of actual cash. We go deeper on this specific gap in Lump Sum vs. Annuity: How Lottery Jackpot Payouts Actually Work.
Why There's No Cap — and Why It Always Eventually Resets
Powerball and Mega Millions both removed fixed caps on jackpot size years ago, which is part of why jackpots have been able to grow past $1 billion and even $2 billion in rare, extended winless stretches. But because the underlying odds of matching every number stay exactly the same every single drawing regardless of jackpot size (see how lottery odds actually work), a jackpot is mathematically guaranteed to eventually be won and reset — it's just a question of how many drawings that takes, which is inherently unpredictable.
The Practical Takeaway
A jackpot's size tells you how long it's been since anyone won and how much attention (and ticket sales) that streak has attracted — not anything about how "due" the next drawing is. The mechanism is straightforward rollover math and a media feedback loop, not a signal about odds, which stay fixed at exactly the same number every single draw, whether the jackpot is $40 million or $2 billion.