This makes complete sense to me as I’ve experienced the results of this graph in my own life. When we’re in a relationship, we spend less time in front of a computer and more with our favorite partner and end up spending money. If you use the computer to make money, then spending this time away from the computer will lower your income.
The reverse is also true of course, that when you’re single, you spend more time at the computer and your income goes up.
All of which is summed up in this crappy graph. See more crappy graphs, done by Brian Shaler.