The US Powerball lottery requires players to choose five numbers from a pool of 69 numbers, as well as an additional Powerball number from a pool of 26 numbers. Since there are so many combinations that might be created using these criteria, it is extremely unlikely that any one ticket will match all of the winning numbers.
The Powerball jackpot's odds of being won are infamously slim. Matching all five major numbers and the Powerball number has a chance of 1 in 292 million. This means that the odds of winning the jackpot are extremely low for each ticket purchased.
As the jackpot develops to a large size, more people are inspired to play the lottery, including those who do not normally participate. As more players compete for the same prize, the odds of winning decrease even further.
When no one wins the Powerball jackpot in a given drawing, the reward money rolls over to the following drawing, raising the total jackpot amount. This can result in even larger jackpots, but also higher odds as more players are drawn to the game because of the massive payout.