I thought Napoleon said it. But no, it's in Adam Smith's Wealth of Nations (1776), book IV, section vii, part 3 (about half way through). Here's what he says:
To found a great empire for the sole purpose of raising up a people of customers may at first sight appear a project fit only for a nation of shopkeepers. It is, however, a project altogether unfit for a nation of shopkeepers; but extremely fit for a nation whose government is influenced by shopkeepers.
We might want to add news-mongers, phone hackers, cops on the take, MPs slurping up the lard at the trough, all the bankers and the other high net worth individuals.
But what was Adam Smith on about?