There was an interesting chart linked from here a couple of months ago, sadly I didn't bookmark it. It showed that the bottom decile of entrepreneurs earned less than the bottom decile of employees. The top decile eared a lot more than the top decile of employees. Everybody else was roughly equivalent.
It seemed most of the entrepreneurs were happy with this, business wasn't a get rich scheme for them, rather a way to avoid traditional employment.
The reason is that, contrary to what the media might sell, "Small Businesses" make up the majority of Entrepreneurship (particularly in the Developing Nations) and this data might shed some insight on it. Entrepreneurship does NOT mean "go big or go home". It is basically setting an acceptable and steady level of income which gives one the necessary autonomy over one's own life. All mom-and-pop businesses fall under this category. I would love to look at some data on the size of this "Economy" which is often ignored completely.
It's not as drastic as I expected. It's mostly unincorporated income that's worse (freelancers, hairdressers, corner shops). They're mostly people who try to escape work even if it means a lower salary.
The incorporated businesses earn more money across the board.