The question comes down to how the effect of a tax cut is measured. Under what is called static scoring, changes are judged without assuming any difference in growth. Under what is called dynamic scoring, assumptions are made about how much growth will change. “Under dynamic scoring, this will pay for itself,” Mr. Mnuchin said at a public forum last weekend. “Under static scoring, there will be short-term issues.”

If you assume it will work, you've got no problems! Clap if you believe in supply-side fairies! Clap your hands!

(Arthur Laffer) said that he would urge Mr. Trump to close loopholes and eliminate tax shelters as he slashed rates, but that even without doing so, a corporate tax rate cut would generate cascades of tax revenue. The businesses themselves would no longer look for ways to avoid paying, and so report more of their income.

"Hey, Joe - know how our effective tax rate is zero but our rack rate is 35%? Trump just dropped it to 15%. I was thinking we should tell our accountants to go fishing because, you know, why get greedy?"

"You're right, Bob. Our cup truly runneth over. BRB, prepping a statement to the shareholders."

(riotous laughter)

"Oh, god, we slay us. See you at the club, Jim?"

"Sure thing, Bob, soon as I get done with these layoffs."