How many credit cards do you have in your wallet?

A key driver of the evolution of frequent flyer programs into frequent buyer programs has been the use of program-affiliated credit cards, which allow cardholders to earn free trips by charging purchases of, well, anything that can be charged.

We know that credit card use is the second largest source of miles, after flights. But there’s a lot that we don’t know.

I’m in the process of trying to quantify the credit card portion of airline programs: how many (and what percent of) program members have mileage cards; how often are those cards used; and how much is charged to them annually? How are those numbers changing over time?

As is often the case with data that might be considered proprietary or otherwise competitively sensitive, the companies with the answers—the airlines and the credit card issuers—aren’t anxious to disclose performance stats.

I did come upon some related stats today on the Experian website that shine some light into the otherwise murky area of credit card use, albeit not mileage cards specifically.

First, the big number: on average, each U.S. consumer has four credit cards. More than half (51.3%) have two or more cards, and 14.1% have 10 or more cards.

Used responsibly, credit cards are a nifty convenience. But according to the Experian figures, 14.3% of credit cardholders are using at least half of their available credit. Since that group also has a higher-than-average number of credit cards—6.6 per person—it follows that they are paying high interest rates on significant outstanding balances.

Returning to the subject of mileage cards, I’m personally down to two cards—one awards airline miles, the other generates a cash rebate deposited into a mutual fund account. The airline card has a hefty annual fee; the rebate card is fee-free. Airline miles are a hassle to redeem; the rebate is hassle-free. Guess which card I’m on the verge of canceling?

The airlines may not be willing to answer my questions regarding the current and past performance of their program-affiliated credit cards. But if my own behavior is any indication, that performance is about to take a turn for the worse.