That's interesting, I didn't notice it. It looks like the bottom income level is primarily people who took a business loss.

As for my confusion, I'm only looking at people near or below the US poverty line. Business owners who take a loss are defined by the government as living in poverty. You might argue that the government overstates poverty, and I would agree with you.

As for the sources of income section, it is clearly incomplete. If it weren't, consumption would be equal to income + change in net worth.