It depends on their priorities. Prior to the cuts to the IRS in the Trump administration, their priorities were in auditing wealthier people and they had an excellent rate of return. Quite obviously even though rich people have lawyers to push back and more sophisticated tax hiding schemes, the payoff when you succeed is huge. And even though you need a well staffed, competent team, it’s still cheaper than the manpower clawing back a few thousand dollars each from tens of thousands of tiny audits.

Are they catching the biggest Panama-paper level players? No those people have too much sway. But they can be very effective against the “ordinary” rich people.