During the first half of the year, consumers cashed in about $29 billion from their maturing certificates of deposit to pay down credit cards and lines of credit.

From January to June, consumers pulled out nearly $200 billion from their CDs, according to research firm Market Rates Insight. About $171 billion was moved to liquid accounts such as money market, savings and checking accounts.

Total consumer debt, both revolving and non-revolving, decreased $29 billion from January to June, MRI noted. The lion's share of the decrease in consumer debt during the same time period occurred in credit cards and other revolving credit. It went from $859 billion to $832 billion--a decrease of $27 billion.

An analysis of the correlation between CD balances and credit card balances indicates a very strong and significant linear relationship, which means that when balances of CDs go down, credit card balances go down and vice versa, said Dan Geller, executive vice president of MRI.

Long-term CDs maturing now are offered at a fraction of the interest rate they originally carried. For example, a three-year $10,000 CD that was opened in September of 2007 at the national average rate of 4.32% can now be rolled over for three more years at the national average rate of 1.80% , a 58% reduction in the return value, Geller explained.

"We are seeing some of the implications of the low interest-rate environment," he said. "As a result, some consumers are opting to cash in their maturing CDs, and pay high-interest credit card balances."