I think this statistic may be misleading. The article states that most of these are "correspondence audits", described as "essentially a letter from the IRS ask

I think this statistic may be misleading. The article states that most of these are "correspondence audits", described as "essentially a letter from the IRS asking for documentation on a specific line item on a return." The headline statistics gives the impression that the IRS spends proportionally more money and effort on auditing poor families. But sending out a letter is easy and cheap. I realize now that the total number of audits may not be a good proxy for cost and effort if not all audits involve an IRS agent coming to your house and trying to guess the value of your artwork.