You would use Statistics!
But I'm not an economist and even an economist finds it difficult to wade through the huge amounts of data to reach sensible decisions.
That is why I like what Gapminder is doing with statistics. Visualizing it so that I can understand it better.
Take a look at the demos and videos at gapminder.org
Of course, I am sure with enough effort you can get statistics to mean whatever you want it to. ;)