How does one even begin to model things like this?
Econometrics is the science of modeling the economy. But like you said it's pretty much impossible to get calculations correct.
The graphs there give you an idea. Just imagine them with 1700 inputs and many 1000s of interactions.
Ray Dalio
Self made macro hedge fund manager with a rags to riches story. He's pretty strange and employs an army of financial engineers in some forest in Connecticut to model this stuff (and make billions of dollars in the process).
Oh, and forgot to mention, it's now the largest hedgefund in the world.