Since the Civil War, without a doubt. I'm still looking for older data.

How much data would it take to convince you?

Debt-to-GDP, 1834-2020. Debt data from Steve Keen, FRED. GDP data from Measuringworth.

 

... those basic economic tendencies ... proceeded steadily ever since long before the Civil War, and continued down to the latest moment ...

- Sidney A Reeve, Modern Economic Tendencies (1921)

 

Why does it matter? Because the cycle of civilization is just a big business cycle. And because when we say "the economy changes" we are talking about that big cycle.

And because we can continue on, to the rapidly-approaching Dark Age, or we can prevent that outcome. The choice is ours. "Civilizations die by suicide".

Excessive preoccupation with finance and tolerance of debt are apparently typical of great economic powers in their late stages.

- Kevin Phillips, quoted by Giovanni Arrighi