Why have there been so many massive Powerball, Mega Millions jackpots recently?

*For previous coverage of the Mega Millions jackpot, watch above.

(NEXSTAR) — Yet again, another huge lottery jackpot keeps growing. This time, it's Powerball, and the current jackpot sits at $747 million. If a player wins Monday's jackpot, it will rank as the fifth-largest Powerball jackpot and the ninth-largest U.S. lottery jackpot.

Earlier this month, someone hit the $1.35 billion Mega Millions jackpot. That prize is the fourth-largest in U.S. history.

Why does it seem like there are so many record-setting lottery jackpots recently?

It's largely due to how the games are structured.

Both Powerball and Mega Millions are designed to go multiple drawings without a jackpot winner — jackpot odds are 1 in 292.2 million for Powerball and 1 in 302.6 million for Mega Millions. If there were frequent jackpot winners, the games would never be able to build to these record-setting levels.

Certain rule changes — Powerball changed the main pool of numbers from 59 to 69 and the Powerball pool from 35 to 26 in 2015, and Mega Millions changed its main pool from 75 to 70, and Mega Ball from 15 to 25 in 2017 — have also had an impact.

"It was, by design, to fuel bigger jackpots," Carolyn Becker, deputy director of public affairs and communications for the California Lottery tells Nexstar. By changing those matrices, the odds of winning the jackpots changed. "That was the intention of those changes."

Powerball has also benefitted from a more recent change. In 2021, the game added a third drawing day, Mondays, giving the jackpot more chances to roll over and grow.

For example, November's world-record Powerball jackpot worth $2.04 billion was finally won (it hasn't yet been claimed) after 41 consecutive drawings over three months. It took 26 consecutive drawings over another three months of game sales for the Mega Millions jackpot won two weeks ago in Maine to reach a record-setting $1.35 billion.

Lottery officials also use sales numbers between drawings to calculate the jackpot (that's part of the reason why it's referred to as an "estimated value").

It isn't just ticket sales that impact the jackpot's size, however, but also inflation and interest rates.

Winners of both Powerball and Mega Millions jackpots have two options to claim their prize - cash (which is always listed separately from the estimated jackpot) or annuity. Powerball officials review interest rates when calculating the jackpot, and Mega Millions officials rely on that day's 30-year U.S. Treasury rate to calculate their game's jackpot prize.

As Becker explains, rising interest rates sparked by record inflation have also led to greater purchasing power. While the lump sum, cash payment of the lottery exists and is real, the advertised lottery jackpot refers to the annuity option.

"If [winners] take the annual payments, which happens far less often, then we invest their winnings and pay them annually," Becker says. The money is invested conservatively into U.S. Treasury bonds, she continues. "So when the interest rate is higher, our purchasing power is stronger."

Those jackpot amounts advertised ahead of the drawing also play an important role - they're advertising for the game. Larger prizes tend to draw more players, and more ticket sales (real and forecasted) lead to bigger estimated jackpots. Victor Matheson, an economics professor with the College of Holy Cross, tells CBS News that Americans are 15 times more likely to buy a lottery ticket when the jackpot nears $1 billion than when it's at $20 million.

There are many factors that can impact sales as well. Becker notes that in California, for example, lottery sales increased during the pandemic while many other forms of entertainment were unavailable.

Still, as nice as the Powerball or Mega Millions jackpot may look, you have better odds of being attacked by an alligator in Florida or struck by lightning than winning either of the top lottery prizes.