Betting

"I'm still betting on you."

- Cinna

The Hunger Games are a major source of gambling and produce intense betting, both in the Capitol and the Districts. Katniss mentions people from District 12 betting on the two tributes Reaped, such as their ages, whether they're Seam or merchant, and if they cry after being picked. In the Capitol, betting takes place throughout the Games, starting before training and increasing in intensity until a victor is determined. Some people close to the Games, such as head stylists and presumably Gamemakers as well, aren't allowed to bet. Cinna says he's not allowed to bet, but that if he could he'd put his money on Katniss.

74th Hunger Games
Betting plays a role in how the tributes conduct themselves. Katniss tries to appear strong in the arena, because "who's going to bet on a tribute who keeps sniveling over the deaths of her opponents". Katniss thinks to herself how the betting gets really hot in the Capitol after the final eight when they do family interviews. Peeta, when realizing Katniss intends to go to the Feast in spite of her telling him otherwise, tells her to never bet at cards, as "you'll lose your last coin".

Betting Odds in Movie
The movie gives examples of betting on the Hunger Games, showing wager stations and the odds of each tribute to win. One odds board pictured was titled "Morning Line Odds", a term based on horse racing. Odds are continually updated over time, where the odds for a tribute can be seen increasing or decreasing. Training scores are important because they give the audience a starting point for betting that will continue throughout the Games. The odds listed for each tribute 3 days and 16 hours before the Games began (multiple numbers indicate changes seen in the film) were:

Katniss and Peeta were given very low odds at first, presumably because they're from District 12 which rarely does well. Rue's odds were originally a very low 60-1, however they soon increased to 7-1. The District 8 male had high odds of 3-1, tied for the highest with Cato.