It doesn't translate to predicting anything, stock market included. Economics is an art, not a science. Society is the petri dish on whch experiments are carried out, and even in the smallest experiments, you can't really isolate environmental variables like you can in say in a physics experiment. Every economic theory is prefaced with "all other things remaining equal", which should invalidate them right then and there.
It's ultimately a study of the impact of the decisions societies make, and even then, the metrics it uses are often poor indicators of quality of life. Apartheid South Africa was the continent's bread basket on the basis of its mining output and high GDP per capita. But that wealth was concentrated in the hands of the white minority and not used to improve infrastructure and education for the colonized majority. That was badly needed to fuel long-term growth and build an economy that wasn't dependent on commodities prices.
