> Things like economies can't grow like that

says who?

if i were born and living in the 1500s, how could i predict the economy would soon grow 10%/year for over a century?

you're just stating things like facts which have never been predictable. nothing about our current growth was inevitable, neither is a gigantic slowdown.

i think these kinds of predictions are:

1. far more difficult than we realise

2. so difficult that there is almost no value in making them.