Although virtually nothing is predictable in politics these days, here is one certainty: Americans — at least the ones watching the news — are about to hear a lot about corporate taxes.

More specifically, one claim will be made over and over again as Republicans ramp up to overhaul the tax code: The U.S. has the highest corporate tax rate in the world. President Trump said it in a Thursday speech in West Virginia, and House Speaker Paul Ryan mentions it a lot.

The claim: The U.S. has the highest corporate tax rate in the world.

The short answer: That is generally true, though many businesses end up paying far less than the statutory rate.

The long answer: The U.S. has the highest top corporate tax rate at least among advanced economies. Compared with nations in the OECD — the Organization for Economic Cooperation and Development, a group of highly developed countries — the U.S. has the highest top corporate tax rate in the world. The top corporate tax rate in the U.S., a combination of federal and state and local taxes, is nearly 39 percent this year. That's well above most other OECD nations.

Trump would like to lower the corporate tax rate to 15 percent, and Ryan has reportedly said that 20 percent to 25 percent is more realistic. Either way, doing so would pull the U.S. well away from the top of this list.

Anyway: The "mostly" in the "mostly true" here comes from the fact that a couple of other places beat out the U.S., outside of OECD countries. According to the right-leaning Tax Foundation, the U.S. comes in third out of 188, behind the United Arab Emirates and Puerto Rico. (Tax Foundation's list includes some U.S. territories.)

However, it's not quite that simple. Those rates above are the statutory rates — the rates set by law. And that is not the rate that many companies in the U.S. end up paying. Deductions and credits help push down businesses' total tax liability, meaning that many companies end up paying far less than the statutory rate. Here is the average effective tax rate for U.S. corporations.

The U.S. is still toward the top of the spectrum, but it's nowhere near the ultra-high level (relative to other countries) that the statutory rate is at.

When many politicians talk about overhauling the tax code, both on the corporate and income side, they talk about this discrepancy between effective rates and statutory rates — the phrase often used is "broaden the base, lower the rates" (or some configuration thereof). The idea is to lower the statutory rates but close some of the loopholes that push those effective rates so far from the statutory rates.

One other way to put corporate tax rates in perspective: the total size of corporate revenue. That has fallen off over time.

And on this measure, U.S. corporate taxation isn't all that big compared with other countries'. As of 2014, U.S. corporate tax revenues were at around 2.2 percent of the GDP. The OECD average was 2.8 percent.

Likewise, the share of government revenue as a whole that comes from corporations has fallen off over time, a fact that Sen. Bernie Sanders highlighted on the presidential campaign trail — the idea being that the government has grown less reliant on corporate tax revenue.

There are a number of factors at play here. The top corporate tax rate has been lowered over the years, for example; in the late 1960s, it was as high as 52.8 percent.

But it's also true that over time, businesses have increasingly paid taxes through the income tax code, as the Tax Foundation points out. "C-corporations" pay corporate taxes, but "S-corporations," also known as "pass-through entities," pay through the individual income tax code. S-corporations include many small businesses run by middle-class Americans, but some very wealthy Americans, including Trump, also own S-corporations, as the New York Times pointed out this spring.

Copyright 2017 NPR. To see more, visit http://www.npr.org/.