The Economist put out an interesting chart highlighting how long it takes to earn $1 million dollars (before tax), based on the median household income from various countries around the world.
 

via The Economist.

Given the median US household income is roughly $52,000, it will take roughly 19.3 years for the typical household to earn $1 million gross. That’s pretty good, relatively speaking.

Of course, it’s not what you make, it’s what you keep. So, savings and tax rates matter here too.