(MONEY Magazine) – The Fed's steady stream of rate hikes continues to push up yields on all cash accounts, but not evenly. Among the biggest jumps: Rates on taxable money-market funds have more than doubled over the past year to an average of nearly 4% and now pay 1.4 percentage points more than the average tax-exempt money fund. A year ago the gap was only a quarter of a point. Why have tax-frees lagged? Their yields are set by supply and demand in the tax-exempt market, while taxable funds closely track general interest-rate moves. As a result, if you're in the 28% bracket or lower, you should look again at taxable money funds. To check which type of fund is best for you, divide the tax-exempt yield by one minus your tax rate. The result is the rate your taxable yield needs to beat. --CAROLYN BIGDA

SAVINGS NOTES AND SOURCES: CD and money-market account data as of Jan. 17 from 100 Highest Yields ($124 for 52 issues; 800-327-7717). Average tax-exempt and taxable money-market fund yields for the week ending Jan. 17 from Money Fund Report (imoneynet.com); all have a minimum investment of $10,000 or less and assets of $25 million or more. Average bond fund yields for the month ending Dec. 31 from Lipper; all are medium- and high-quality funds without sales loads and with average maturities of three years or less. [1] Manager absorbed all or some operating expenses. [2] Closed to new investors, except Bank of America customers.

CREDIT NOTES AND SOURCES: All rates subject to change. Credit-card rates are for standard cards as of Jan. 17 from Bankrate.com and are variable unless otherwise indicated. Survey does not include Internet-only cards or AmEx Blue. [1] Visa only. [2] Fixed rate. [3] MasterCard only. [4] Platinum and gold cards.