Retirement confidence among American workers has reached a four-year low, according to the Unretirement Index, a poll of nearly 1,500 working Americans by Sun Life Financial Inc. After remaining stable for three years, retirement confidence dropped nearly 20 percent in September compared to the prior year.

The Unretirement Index measures five components, all of which dropped since last year. Nearly 32 percent of those surveyed said they were not confident about the benefits they needed to retire, including defined benefits plans and employee health benefits.

Only 23 percent of those polled felt confident they would meet basic living expenses in retirement, compared to 42 percent in 2010. One in five working Americans say they will never retire and confidence in the future of Social Security plunged to 9 percent in 2011, compared to 22 percent in 2008. Confidence about Medicare benefits also has plummeted to 8 percent in 2011, from 20 percent in 2008.