Do you remember flat taxes? They used to be the Next Big Thing in economics. The idea was that by merging all its tax bands and removing any loopholes and exemptions, a country could levy one low tax rate on everyone. And here’s the kicker: not only were flat taxes supposed to be far simpler and more avoidance-proof than today’s convoluted systems, they could even raise more money.

Or so went the theory. And in some cases that was precisely what happened. In many of the countries where flat taxes were introduced, including Estonia, Latvia, Lithuania and Russia, government revenues actually increased, though sometimes at the expense of rising inequality.

But whenever overexcited think tanks advocated something similar over here, they found themselves colliding with