More U.S. workers plan to invest their tax refunds this year, a significant change from previous years, reports Principal Financial Group, Des Moines, Iowa.

A study by Principal found a marked decrease from previous surveys in the number of workers who said they’ll spend their refund on big-ticket items (7%, down from 16% percent in 2003). Only 44% said they’d use it to pay down short-term debt, down from 50% in 2003.

But there was a striking increase in those who said they plan to save and invest their refund this year–38%, up from 31%.

Principal’s Financial Well-Being Index survey also showed 84% of workers expect a federal or state income tax refund this year, about the same as in previous years. The index surveys American workers at small and midsized businesses (firms with 10 to 1,000 employees), and is conducted for the Principal each quarter by Harris Interactive.

For workers who participate in flexible spending accounts, the study also examined how accurately they have estimated expenses such as medical or dependent care expenses for reimbursement.

The study found 44% estimated their actual medical expenses within $100 in 2005. Another 39 percent underestimated their medical expenses and therefore did not set aside enough pretax dollars in their FSA accounts, while 16% overestimated expenses and consequently could lose funds.