February 18th, 2023, 1:35 pm
I don't think anyone has ever dared to try to fit numbers into the relationship. Possibly for good reason, because it all probably depends very heavily on what your starting point is: are you going, for example, from 1% to 2% interest, or from 7% to 8%? And that's without looking at the prevailing rate of GDP growth.
If I had to come up with numbers -- at gunpoint, for example -- I think I'd start with thinking about what the "multiplier effect" of fiscal stimulus is, mainly because there are a lot more hard number guesses at that ... even if they have all turned out to be completely wrong.
Then I'd make a guess at what might be thought of as the duration of borrowing: if we assume there is a fixed amount consumers plan on repaying at a fixed date in the future -- both of which are obviously wrong assumptions, but never mind -- how much does a 1% increase in the interest rate change the amount of money that people will borrow?
And then pretend, wrongly, that the change in the amount borrowed is a change in the amount of fiscal stimulus, and hit it with your inaccurate guess at the multiplier effect, and you get a really bad guess at the effect on GDP.