I have discovered a way to carry a credit card balance indefinitely, interest-free, without making payments, using only an Amazon Kindle.

How my card works is, any purchases made during Month N get applied to the balance due in the middle of Month N+1. So if I make a purchase now, in May 2013, it goes on the balance due June 15th. If I don't pay the full May balance by June 15th, then and only then do they start charging interest. This is pretty typical of credit cards, I think.

Now the key loophole is that refunds are counted as payments, and are applied immediately, but purchases are applied to the balance due next month. So if I buy something on June 5th, and return it on June 6th, the purchase goes toward the balance due on July 15th, but the refund is applied as a payment on the balance due on June 15th! So you can pay your entire June balance with nothing but refunds, and you won't have to worry about paying for those purchases until July, at which time you can do the whole thing again. The debt is still there, of course, because all you've done is add and then subtract say $100 from your balance, but absolutely no interest is charged. This process is limited only by your credit line (which you cannot exceed at any time) and by the ease with which you can buy and return stuff each month.

Here's where the Kindle comes in. Repeatedly buying and returning items from a brick-and-mortar store is incredibly time-consuming and risky. You have to buy stuff, keep it in good shape, and then return it, interacting with human clerks each time, without raising suspicion. Not efficient. But if you have a Kindle, you know that when you buy a book, after you hit "Purchase" a screen comes up that asks if you have bought the item by accident, and if so, would you like to cancel the purchase. If you hit the button to cancel the purchase, what happens is that the purchase is still applied to your card, but it is refunded a couple of days later. Bingo. Automatic refunds, obtained at home at no risk, with no human oversight.

But e-books on Amazon are like $10, so you'd have to sit there all day hitting "buy" and "return" to shift a significant amount of debt, right? Wrong. If you know where to look, the Amazon kindle store has lots of handbooks, technical manuals, and textbooks that cost hundreds of dollars. Start out searching for "neurology handbook" and just surf the "similar books" list from there. Buy and return a few of those, and you're set for another month.

Obviously you have to pay off the debt at some point. This is not free money. But if you're in a tight spot for a few months, it's incredibly useful. And hey, if the inflation-adjusted prime rate is 0%, why should you have to pay interest? You're good for it.

This is by far the most munchkin-like idea I've ever had, and I'm pretty happy about it. I've been using it since January, making real payments toward my card as I can, and covering the rest with Amazon buy-and-returns. I know I'll pay down the debt when I have a better job, but in the meantime it is really nice not to have to pay any interest on it.

Hm. Still not working for me in FF. My guess is it's a local issue, but I don't know what it would be that would cause both FF and Chrome to mess up...

But at least we finally noticed we're robots, and we can use the skills of rationality to hop off our habit treadmills and pursue our values instead.

How do you determine whether you've really hopped off the treadmill, vs. using higher-order desires as a sophisticated long-term strategy to spread your genes and memes? (Is this covered in the book?)

gwern told me about PB in January 2011, and given my heavy use, I've spent about two days tweaking it and fixing bugs. If you like the changes, feel free to upvote this comment (I could use more than 0 karma). Note that TrikeApps is responsible for making the database faster, not me.

Also, if you see old predictions with bizarre estimates (e.g. 99% instead of 1%), it's because almost everyone made mistakes due the old copy displaying "99% against" instead of "1%" for 1% - the new version doesn't do this.