Once again, following a pronouncement by the IMF, the quote:

The only function of economic forecasting is to make astrology look respectable.

is being posted across the Internet and being attributed to John Kenneth Galbraith. Astrology sometimes being replaced with Meteorology. 

Of course it is a simple matter to verify the source of the quote – but why bother when you can just cut and paste from the first link that pops up on Google?

It belongs to the economist Ezra Solomon.

Oxford Reference

The Times

New Scientist

Etc.