The centerpiece of the new tax law is a cut in the corporate tax rate from 35 percent to 21 percent. Proponents promise the lower rate will bring jobs and investment to the United States and boost economic growth significantly.

There were good reasons to cut the corporate tax rate—for example, our statutory rate was higher than in almost all other countries. But the Tax Cuts and Jobs Act’s corporate tax cut will likely have a much smaller impact on growth than its supporters promise. Here are six reasons why:

The timing is terrible. The economy is doing well, and corporate profits are booming. In early 2017, after-tax corporate profits were about 9.5 percent of Gross Domestic Product, compared to an average of about 6 percent of GDP in the 50 years leading up to the Great Recession. Plus, with the economy close to full employment, businesses can’t produce much more domestically in the short run. A large stimulus now risks inflation.

The plan is expensive. It will cut federal revenues by $1.5 trillion over the next decade, and by more than $2 trillion if the bill’s temporary provisions are extended before they are set to expire, as Republicans insist will happen. If revenue losses are not offset by spending cuts, the increase in government borrowing will reduce future income growth by raising interest rates and discouraging private investment or requiring higher borrowing from abroad.

Lower corporate tax rates mostly benefit old investment and encourage tax sheltering. Cutting corporate rates provides windfall gains to the returns from past investment. These gains benefit existing shareholders, including foreign shareholders, but they do not raise incentives to invest. Most economists favor forward-looking investment incentives such as expensing over rate reductions precisely because these incentives can lead to a larger capital stock. In addition, since the 21 percent corporate tax rate is so much lower than the top individual tax rate (37 percent), there will be a strong incentive for rich people to use corporations as tax shelters.

These rate cuts won’t increase new investment. The TCJA also allows firms to immediately deduct—or expense—the full cost of many new investments. But expensing makes rate reductions much less effective. Here’s why: Expensing by itself brings the effective tax rate for corporations down to zero on new equity-financed investment. In other words, once a firm has expensed an investment, cutting the statutory corporate rate won’t reduce its effective tax rate any further. At the same time, lower corporate tax rates raise the effective tax rate on new debt-financed investment, as Larry Summers and Jason Furman have pointed out.  If—as some analysis suggests—debt is more internationally mobile than equity, then a cut to the corporate tax rate plus full expensing could actually reduce new investment.

The TCJA may encourage, not discourage, overseas investment. By generally exempting the foreign profits of multinationals from US corporate income tax under a so-called territorial tax system, the TCJA will encourage US companies to locate investment, jobs, and reported profits overseas—just the opposite of its intended goal. A well-designed international taxation regime could stem this flow, but the anti-abuse provisions in the new tax bill are so poorly designed that they might magnify the present incentives to move economic activities offshore.

The rate cuts will encourage other countries to follow suit. Any advantage the US gains from a low corporate tax rate will evaporate as other countries respond by cutting their own tax rates. This happened in 1986 after the US cut its corporate tax rate from 46 percent to 34 percent. In short order, our major trading partners—30 OECD countries—cut their rates even lower. Combined with our new territorial tax system, falling corporate rates overseas will drive more investments and jobs offshore.

Congress could have passed a corporate tax reform that might have avoided all these problems. It could have chosen from several ideas already on the shelf.

For example, it might have lowered the corporate rate to a more realistic 28 percent, a level that could be fully financed by eliminating most corporate tax expenditures. This would have made the US corporate income tax more efficient and avoided higher deficits, though it would not have solved the problem of US firms chasing the lowest rates around the world.

A more ambitious proposal by our TPC colleague Eric Toder and AEI scholar Alan Viard would retain a small corporate tax but tax most profits at the shareholder level. By primarily taxing investors, this structure would prevent firms from seeking low corporate rates overseas.

House Republicans proposed a destination-based cash-flow tax in 2016, which would have eliminated the incentive to shift profits and production overseas. It was a type of Value-Added Tax with a deduction for labor costs, repackaged to look like a business income tax.  Alternatively, if Congress could overcome its VAT-phobia, it could adopt a more standard form of consumption tax and allow individuals to claim a progressive tax credit on earnings—kind of a universal Earned Income Tax Credit.  This could be designed to be progressive and pro-growth without busting the budget.

Despite the hype, tax reform doesn’t have to be a once-in-a-generation opportunity. This bill raises the odds of a second major tax bill before too long: the public might demand change when they see the actual economic effects of TCJA (as they did after the 1981 tax cuts led to a wave of tax sheltering and giant deficits) and the expiration of all the individual income tax breaks in 2025 could produce another opportunity. Let’s hope that policymakers will adopt some real reforms next time around.

William G. Gale is co-director and Leonard Burman is director at the Urban-Brookings Tax Policy Center. This article originally appeared here.