One of the things Hillary Clinton and Donald Trump disagree most strongly about is how to stimulate the economy. Donald Trump has one idea that conservative economists would probably agree with: He wants lower taxes.

“We're going to cut taxes massively. We’ll cut business taxes massively. They’re going to start hiring people. We’re going to bring the $2.5 trillion that's offshore back into the country,” Trump said in the third debate. “We’re going to start the engine rolling again because right now our country is dying at 1 percent GDP [growth].”

More specifically, Trump has said that he wants to lower taxes for corporations, from 35 percent to 15 percent, so that the nation’s economy can grow again. When companies pay lower taxes, the thinking goes, they have more money to spend on research and development, hiring, and producing things—all of which can lead to growth.

After all, the United States has the third-highest tax rates on corporations in the world, according to the nonpartisan Tax Foundation, and there has been no shortage of examples of companies such as Apple moving parts of their operations to other countries to avoid paying such a high rate.

So would lowering the tax rate bring companies back to the U.S., create jobs, and stimulate the economy? Economists are divided on this. On the one hand, if companies get to pay lower taxes, they have more money to invest in new innovations and perhaps more hires. Lower taxes could entice new companies to settle in the U.S., and could convince companies that have offshored some of their business to bring those parts back. But on the other hand, cutting taxes doesn’t necessarily mean that companies will create jobs—they could just hold onto the extra cash or distribute the profits to shareholders and those at the top.

Luckily, there is more to go on than just theory. There have been two real-world experiments in which developed countries cut their corporate tax rates in an effort to stimulate economic activity: Ireland’s tried it and so has Great Britain. Ireland for decades has touted its low tax rates as one of the reasons its economy has flourished. Its corporate tax rate, at 12.5 percent, is the one of the lowest in the developed world. Perhaps inspired by Ireland’s success, the Conservative Party in the United Kingdom, after being elected to lead the government in 2010, began to cut corporate taxes in the U.K., lowering the rate from 28 percent to 20 percent between 2010 and today. The architects of the plan say they intend to further lower the tax rate to 15 percent.

So how did lowering corporate taxes work out for Ireland and Britain? Was the policy a boon to their economies? Did it create the growth spurt that developed Western economies are desperately seeking these days? The short answer: Perhaps, but that doesn’t mean it would work for the U.S.

In Ireland, for instance, the economy is booming, at least by some measures. The country’s gross domestic product grew at a rate of 26.3 percent in 2015, which is a staggering figure, especially when compared to the growth rate of the United States, which in 2015 was 2.4 percent. Companies including Microsoft, Google, Apple, and Adobe all have subsidiaries in Ireland in order to take advantage of the country’s tax rates and permissive tax code. Ask the Irish government, and it will tell you that low corporate tax rates are one of the reasons Ireland is doing so well. “Our competitive rate of corporation tax has been an important part of our industrial policy since the 1950s, and has attracted real and substantive operations to Ireland since then,” Grainne O’Rourke, a press officer for Ireland’s Department of Finance, wrote me in an email.

According to a study by the nonpartisan Economic and Social Research Institute (ESRI), Ireland’s corporate tax rate has been successful in attracting foreign companies to invest in Ireland. If Ireland changed its rate from 12.5 to 13.5 percent, the study found, it would reduce the likelihood of companies choosing it as a location for foreign direct investment by 4.6 percent.

Still, GDP isn’t everything. After the release of Ireland’s latest GDP figure, some economists called the metric “meaningless.” That’s partly because some of the growth in GDP is owed to the fact that companies such as Apple last year had to pay higher taxes, producing more money for the government. This highlights the fact that many of the profits reported in Ireland don’t necessarily have to do with the on-the-ground business of companies located there, but rather with the accounting of those companies.

In short, Ireland’s tax code, which allows companies to use maneuvers like the “double Irish” to port profits from country to country to avoid taxes, is what is most important, not Ireland’s rate, said Jim Stewart, a professor of finance at Trinity College, Dublin. Ireland’s corporate tax rate may be 12.5 percent, but very few companies actually pay that rate, since they can use accounting strategies permitted in Ireland, Stewart told me. They tend to pay a rate that’s much lower, he said, and contribute far less to the economy than Irish companies that don’t have a multi-national presence.. “The problem is the nature of the companies attracted to Ireland,” Stewart said. “If you are here for tax reasons, you have a particular kind of operation in Ireland—with few linkages with the local economy.”

The tax strategies allowed in Ireland fell under public scrutiny a few years ago when the U.S. government began to investigate how Apple was using Ireland and other offshore locations to avoid paying taxes in the U.S. “Ireland has essentially functioned as a tax haven for Apple, providing it with minimal income tax rates approaching zero,” a Senate report concluded in 2013. In August, the European Union ordered Ireland to collect $14.5 billion in unpaid taxes from Apple; Ireland is appealing the ruling, saying it doesn’t want the money from Apple.

Even if Ireland’s economic growth is more than just companies shifting their profits to the nation for tax purposes, the growth can’t all be attributed to the country’s tax rate, according to Nicholas Shaxson, the author of Treasure Islands: Tax Havens and the Men Who Stole the World. There are other factors that have helped jumpstart the Irish economy, he said, and they’d be difficult to replicate elsewhere. “The corporate tax was an ingredient; it was an important ingredient, but it is not the magic elixir for success that so many people point to,” he told me.

For one thing, Ireland’s growth really took off in the 1990s. That coincides with when Ireland joined the European Single Market, which allowed goods and people to flow freely across borders between Ireland and other EU members. This was a boon for multinationals: Ireland became an entry point into the European market. Companies could manufacture goods in Ireland and then sell them elsewhere in Europe without tariffs, or set up a presence in the country and then have access to the whole EU. The fact that Ireland was an English-speaking country gave it a huge advantage over other European-market members, Shaxson said.

What’s more, in the 1960s, the Irish government oversaw a series of educational reforms, which led to a large number of highly educated graduates coming out of Irish schools in the 1990s. That also helped attract companies looking for a foothold in Europe. Essentially, Ireland became in the 1990s and 2000s a country that was friendly to multinationals, where they could access the European market, hire educated professionals, and enjoy low tax rates. So it wasn’t just the tax rates that attracted companies, Shaxson said. In fact, Ireland raised its corporate tax rates a bit, from 10 percent to 12.5 percent, in 2003.

“What happened in Ireland is extremely, exquisitely specific to Ireland,” he said. “It was a whole collection of things that all came together that cannot be replicated by any other country in the world.”

That’s not exactly a strong case for lowering the corporate tax rate in the U.S. So what can be said, then, of the U.K., which has lowered its corporate taxes 10 percentage points in the past decade and plans to further reduce them ahead of the country’s departure from the EU?

This one is more difficult to suss out. In the years leading up to 2010, the U.K. was in recession, and its gross domestic product fell 4.2 percent in 2009. It started growing again in 2010, and has grown every year since then (though this year’s growth has been weak, in part because of fears of Brexit). But it’s hard to attribute that recovery solely to changes in the tax regime, because it came at the same time as the global economic recovery, according to Gavin Ekins, a research economist at the Tax Foundation.

Still, there are some signs that companies are looking at relocating to Britain because of its tax changes. Shortly after the initial rounds of tax cuts in 2011, Ernst & Young said that it was aware of 60 multinational companies looking to move headquarters to the U.K. in the following 18 months. “When you look at a corporation trying to do the best for its shareholders, one of the key issues to address is your tax position,” Ferdinand Mason, a partner at the international law firm Jones Day in London, told me. According to Ekins, at the Tax Foundation, the number of UK corporations may overtake the number of U.S. corporations by 2017.

This is a reversal from when the U.K. had taxes that were about as high as those in the United States, Ekins said. When the U.K. tax rate was 28 percent, a number of companies moved their headquarters to Ireland to avoid the tax rate, according to Ekins. Now, some of those companies are moving back. A lower tax rate, then, could stem the tide of companies leaving the U.S. for cheaper pastures.

But cutting taxes won’t necessarily jumpstart Britain’s economy, said Helen Miller, the associate director of the Institute for Fiscal Studies, in London. The British economy is performing tepidly both because of the Brexit vote and because consumers aren’t buying as much as they used to; cutting corporate taxes won’t mean that consumers will shop more. And the danger of depending on a low tax rate to attract companies is that another country could make its tax rate even lower, thus erasing any advantage. After all, the UK was losing out to Ireland, and now Ireland is losing some business to the UK. According to the ESRI report, when the UK lowers its tax rate one percent, the probability of Ireland being chosen as a location for new foreign-investment projects from non-EU companies fell by 4.3 percent. “You can be special and lure in companies as long as you’re the only one in town doing that game,” Miller said.

What should the U.S. take away from these examples? First off, lowering the corporate tax rate alone won’t necessarily make any difference—there are plenty of other things that shape where companies choose where to locate—an educated workforce, a robust regulatory regime, and access to capital among them. Second, it’s entirely possible that companies can move somewhere for a low tax rate and still create little economic activity and few jobs there. Third, lowering taxes can lead to a race to the bottom in which many countries compete to lower their taxes.

Indeed, the U.S. would see dramatically lower revenues if it lowered its corporate tax rate. This wasn’t a big deal in Ireland when the country designed its tax code, because it had few companies at the time—every company that chose to locate billion-dollar businesses there meant an increase to Ireland’s tax revenues, even if it was just tens of millions of dollars. That money meant a lot to the Irish economy. But the U.S. economy, which is much bigger and already has lots of companies based within its borders, is in quite a different situation: The U.S. would lose revenues from its existing companies if it lowered its tax rate, and potentially only gain small amounts of revenue if new companies chose it as their new home. That revenue wouldn’t provide much of a bump to the U.S. budget.

Perhaps most important, though, is that the U.S. is already home to many companies, despite its high tax rate. Companies locate their operations and employees in the U.S. and (sometimes) pay a 35 percent tax rate, even though that rate is one of the highest in the developing world. Ekins says the the U.S. actually has a favorable regulatory regime for companies, a large number of willing investors, and an extremely productive workforce.

Why limit the tax revenues from those companies if they’ve already committed to staying in the U.S. despite its high taxes?

If there’s any change to corporate tax policy in the U.S. during the next presidency, perhaps it should focus more on making sure companies can’t so easily offshore their profits to places like Ireland and England to avoid U.S. taxes. It’s something the Obama administration has been trying to tackle this year; in June, the Treasury Department released new rules that would take aim at foreign companies acquiring multiple U.S. companies for tax purposes. (If a smaller foreign company acquires a U.S. company, the combined firm can often save money by paying foreign, not U.S., tax rates.) There are many more steps the U.S. can take to try and recoup some of the corporate tax revenues it’s losing out on. This doesn’t necessarily mean lowering the tax rate, but instead changing the tax code so that companies operating in the U.S. actually have to pay its tax rate. It’s not as simple as just lowering the rate, perhaps, but it’s a change that makes much more sense for the U.S. economy.