American retirees still have a steep learning curve when it comes to knowing what they'll need for a financially secure retirement, according to a new survey.

Of the 1,213 pre-retirees aged 56 to 65 who participated in the 2011 MetLife Retirement Income IQ program by taking a 15-question quiz on retirement issues, the majority were only able to answer five questions correctly. The answers indicated a high level of misunderstanding on subjects such as life expectancy, inflation, retirement income/savings, long-term care insurance and Social Security, according to MetLLife.

In the 2008 version of the study, most respondents correctly answered six of the 15 questions.

Only 17% of the respondents knew that delaying the collection of Social Security by three years would add 24% to the amount they receive, according to MetLife.

Only 45% knew that experts believe retirees will need 80% to 90% of their pre-retirement income to maintain their current standard of living. And nearly 30% incorrectly believed that retirees should limit what they withdraw from their savings each year to 7 to 10%, while 11% believed they should plan to withdraw between 11 and 15%. In reality, experts recommend limiting the percent retirees withdraw from their savings each year to 4% to 6%.

On a positive note, MetLife said, respondents recognized that they'll live longer, and that they will be dependent on Social Security and other steady lifetime income for their prolonged retirement.

The respondents' average estimate of what a couple would need in pre-retirement income to cover their essential living expenses (i.e., housing, food, health care, transportation, insurance and taxes) was 61%, very close to informal estimates that about 60% is needed to take care of the absolute basics. Yet, the biggest concern expressed was having enough retirement income to cover them.

"Everyone knows they're likely to live longer, but most don't realize that can mean living past age 85 and they fail to calculate how much money they will need for a steady and lasting income," said Sandra Timmermann, director of the MetLife Mature Market Institute.

-Jim McConville