APR and APY are irrelevant concepts in the world of manufactured spend

When lawmakers decide to crack down on payday lenders, they invariably cite the extortionate annual percentage rate, or APR, charged by those lenders. Wikipedia helpfully provides this example:

"For a $15 charge on a $100 14-day payday loan, the annual percentage rate is 391.34%."

You won't find a bigger defender of consumer rights and economic justice than your humble blogger, but I have to confess that I've grown increasingly uncomfortable with the concept of APR and APY (annual percentage yield) as applied to my own lifestyle.

The important thing to understand is that APR and APY aren't laws of nature: they're accounting identities that are based on the idea of compound interest: if the fees you pay, or interest you earn, is added to your original balance on a daily or monthly basis, then you'll end up paying (or earning) more over the course of a year than you will if you simply multiplied your first month's balance by 12 times the monthly interest rate paid (or earned).

How, then, to account for manufactured spend? Am I earning interest when I take out a "loan" for $1007.90, with a "rebate" of $20.16, then use the proceeds to pay off my loan during its 20-50 day grace period? If so, what's the relevant time period to extrapolate over the 12 month period required for APY calculations?

The Barclaycard Arrival World MasterCard allows immediate redemptions of earned miles, meaning the total turnaround time between earning and redemption might be as little as 3-4 days; using APY calculations I'd end up with something like 202%.

What I'm trying to say is that while this sounds like an epistemological question, it's actually the opposite: it's the question of how to account for certainty.

That's why I'm increasingly inclined to think about manufactured spend not as an investment, with concomitant risk and return, but as a job. It has a more or less guaranteed return depending on the time and skill you devote to it.

You should think about APR when deciding on a mortgage lender, and APY when deciding on a retirement fund, but when thinking about manufactured spend the much more important concepts are revenue and cost.

Personally, my rule of thumb for the bulk of my manufactured spend is that every individual transaction has to be worth it. Of course I run a lot of experiments for the sake of my readers —I redeemed 8,000 Ultimate Rewards points for a roundtrip to Philadelphia on Saturday, and I don't expect to turn on a profit on those points! But if I pay $17.68 for $44.76 in travel redemptions with a Barclaycard Arrival card, I'll call that a $27.08 profit without losing too much sleep over what time period it should be calculated over: a 60% discount on my paid travel is good enough for me, without claiming to have beaten the market with my brilliant "investments."