Premise: You can't pay down debt by using credit.

I want to look at the amount of interest we pay relative to the quantity of money we have "readily accessible for spending".

Why?

It's a measure of how much we rely on credit, and whether we can afford to do that.

Before 1966 or so (when Minsky and Keen say the golden age ended) interest paid was less than half the size of M1 money. By 1974 (when everyone else says the golden age ended, if they even admit there was one)  interest paid was more than all of M1 money. And from 1980 to 2010 (when economists were learning the lie that there never was a golden age) interest paid was on average twice the size of M1 money.

And that's just the interest.