A reward credit card says a lot about the person who wields it. Gas-station card? Road warrior. Airline-miles card? Vacation lover. Cash-back reward card? Penny pincher. (What does my college-savings reward card say? Tuition-fee obsessor.) Most reward-card programs work like this: Buy something with the card and get a percentage of that purchase back in the form of free stuff or a cash rebate ...

In my blog post Wednesday , I offered up a quick primer on how the Federal Reserve's key federal-funds rate -- the interest rate at which banks lend to each other overnight -- influences the interest rates charged on various types of consumer credit lines (mortgages, credit cards, auto loans, and the like). In most cases, a low federal-funds rate translates into lower finance charges for ...