"Available means I've got it"

Start with the green number, because it's the belief the whole habit rests on.

Ask what the limit is. It's a number the card company chose. They chose it by estimating, from your income and your record and their models, how much they could lend you and get back with interest over time. It isn't a description of what you own. It isn't a judgement that you can afford five thousand pounds of coats. It's a commercial decision about how much of their money it's profitable to have out with you, and a person paying interest on four thousand pounds is more profitable than one paying interest on nothing. This is my reasoning about how limits work and not a finding from a study, but I don't think anyone who sets limits would dispute it. The limit is theirs. The green number is the part of their money you haven't borrowed yet.

Hersh Shefrin and Richard Thaler, in 1988, set out an account of how people mentally divide money into accounts. Current income, the money that's come in this month. Current assets, the money that's put by. And future income, the money that's still to come. People treat the three differently, and the temptation to spend is greatest for current income and weakest for future income. An earlier book in this series uses this for saving. I'm using it for the gap, because the gap has been filed in the wrong account. Available credit feels like current assets, money you have and could use. It's future income, the money you'll earn next year and hand over, plus interest, and if it were labelled that way, you'd spend it the way people spend future income, which is reluctantly.

A shop's till roll is a fair comparison for two sentences. Every item goes on it and the total's at the bottom, and if the roll were printed with the total at the top and the items hidden, you'd buy differently, and that's the app.

So "available means I've got it" is a mislabelling, and it isn't yours. The card company chose to put the borrowable amount in green and the owed amount in black and underneath, and the choice does what it's meant to. It makes borrowing feel like having. The two lines from chapter 1 are the correction. Written side by side, owed and available, the green number becomes what it is, the room left before you're stopped, and the black number becomes what it is, which is the coat, and the one before it, and the one before that, with interest.