The current system gets criticism from both the right and the left. Many progressives argue that by letting companies keep profits overseas indefinitely, the system incentivizes them to shift their activities and profits out of the U.S. and into countries with lower tax rates—especially tax havens. Meanwhile, many conservatives and pro-business interests argue that forcing U.S. multinationals to pay taxes on profits they make overseas (after subtracting the taxes they paid to the foreign country) makes them less competitive in foreign markets. There’s also a conservative argument that the system leads companies to stash money in overseas subsidiaries that they might otherwise bring back and invest in the United States if they didn’t get taxed on their foreign income upon repatriation.

Aware of those criticisms, President Obama suggested reforms in 2012 that sought to find some common ground. First, his plan would have imposed a one-time tax on foreign profits that have never been taxed, with all of the proceeds going toward financing a major infrastructure package. (Trump’s proposal has no such infrastructure provision.) Second, Obama sought to lower corporate rates while at the same time eliminating enough loopholes so that the overall amount of taxes that corporations pay wouldn’t change and the deficit wouldn’t increase. (Under Trump’s plan, the net tax cut to corporations is about $2 trillion over 10 years, according to an estimate from the nonpartisan Tax Policy Center.)

And third, Obama proposed a per-country minimum tax on foreign profits, meaning that there’d be a baseline rate—19 percent was what he put forward—that all companies would be required to pay on foreign profits, even if their operations and earnings were coming from countries with extremely low rates. Thus, if a U.S. company booked profits in a tax haven with a corporate rate of only 5 percent, that company would be taxed that year at a rate of 14 percent by the the U.S. government, for a total rate of 19 percent. The idea was that a per-country minimum tax would make it useless for a company to spend time and money shifting profits to tax havens.

The Trump-GOP plan will also propose a minimum tax rate on foreign income, according to multiple reports. But whereas Obama’s plan (which ultimately didn’t become law) assessed a company’s taxation in each country individually, the Trump framework would come up with an average for all foreign earnings combined, a so-called “global minimum.”

This might seem like a small difference, but the design of their global minimum tax creates perverse incentives for companies to offshore jobs and shift profits to tax havens—outcomes that a per-country minimum tax would avoid. How? Consider two examples, assuming for simplicity that the GOP plan would impose a domestic corporate tax rate of 20 percent (as the Treasury has said it will) and a rate of 10 percent on overseas earnings (it’s expected to be in the range of 10 to 15 percent, but that won’t be known for certain until Thursday). Say there’s a company with two branches that each produce $100 million in profits a year, one in Minneapolis that faces the domestic rate of 20 percent and one in Bermuda, a country that has a corporate tax rate of zero. If the GOP plan used Obama’s per-country-minimum approach, the company would pay $20 million in taxes on its profits in Minneapolis and $10 million on its profits in Bermuda. In total, the company would pay $30 million on $200 million of profits.