(AP Photo/Bernd Kammerer)

Many U.S. workers are playing what amounts to a game of income roulette without understanding much about the nature of the game.

Researchers at Unum Corp., Chattanooga, Tenn. (NYSE:UNM), and the American College, Bryn Mawr, Pa., workers’ problems with understanding the odds in new reports.

The researchers at Unum note that typical workers think injuries are the health problems most likely to lead to workers missing work.

In reality, Unum says, an analysis of Unum’s own long-term disability (LTD) insurance claims data shows that injuries accounted for a little more than 10% of the LTD claims filed in 2011.

Cancer was the most common cause of LTD claims. It was responsible for 15% of the claims.

Back disorders not resulting from injuries ranked second. They led to a little less than 15% of the claims.

At the American College, researchers commissioned a survey of 1,600 employed U.S. residents ages 25 to 64 with household income of at least $35,000.

Many workers who took a disability literacy quiz had a hard time understanding how common disability is, college researchers say.

Experts estimate today’s 20-year-olds have a 26% chance of suffering a short-term or long-term disability before they reach the normal retirement age.

About 51% of the women surveyed and 57% of the men said they thought their chance of becoming disabled before they retired was less than 5%, the researchers say.

Only 15% of the participants said they had much concern about the possibility of being disabled for a year or more.