The 29 lotteries that participate in the Powerball (search) game have voted to make changes that will increase the size of the average jackpot but decrease the chance of winning.

Starting Aug. 29, the beginning jackpot will increase to $15 million from the current $10 million, the Multi-State Lottery Association (search) announced Wednesday. The top prize will grow by no less than $5 million between each drawing.

To further boost jackpot size, two numbers will be added to the first pool of the game, meaning players must correctly choose five numbers ranging from one to 55, up from 53.

The Powerball is drawn from a separate pool numbered from one to 42. That will not change.

The larger number in the first round decreases the chances of winning the jackpot to 1 in 146.1 million. The current game has jackpot odds of 1 in 120.5 million.

Ed Stanek (search), Iowa Lottery chief executive and one of Powerball's co-inventors, said the changes are part of a popular product's evolution.

"Players tell us they expect large jackpots in the game and we will continue to deliver those," Stanek said.

Another change in August will be to double the prize for those players who match the first five numbers but miss the Powerball. They'll win $200,000 instead of the current $100,000.