The 2017 Tax Cuts & Jobs Act included a little-known provision establishing something called opportunity zones. The plan, which was lauded as a way to direct investments into under-developed communities in the U.S., created 8,764 tax havens that were almost immediately exploited by the wealthy to gobble up capital gains tax breaks. Pulitzer Prize-winning journalist David Wessel explains how opportunity zones came to be, who is profiting off of them, and why it’s so difficult to tweak the tax code without creating windfalls for the rich.