Over and over again, President Donald Trump has touted his tax proposal as the biggest ever.

On Oct. 25, he tweeted, "Working hard on the biggest tax cut in U.S. history. Great support from so many sides. Big winners will be the middle class, business & JOBS."

Working hard on the biggest tax cut in U.S. history. Great support from so many sides. Big winners will be the middle class, business & JOBS — Donald J. Trump (@realDonaldTrump) October 25, 2017

That same day, he told Lou Dobbs of the Fox Business Network, "We’re bringing the corporate rate down to 20 percent from 35 percent. ... This will be the biggest tax cut in history. In the history of our country."

But is it? Tax experts say no. (The White House did not respond to our inquiry.)

The current tax proposal is still a work in progress, but the Senate budget resolution allows it to reduce federal revenues by $1.5 trillion over 10 years. An estimate by the Committee for a Responsible Federal Budget suggests that, when all is said and done, the reduction in tax revenues will increase to $2.2 trillion over 10 years.

So based on what we know now, the tax proposal will probably amount to between $150 billion and $220 billion per year.

That doesn’t stack up as the largest cut ever.

The Treasury Department has published a list of the biggest tax bills between 1940 and 2012, measured not only by contemporary dollars but also by inflation-adjusted dollars and as a percentage of gross domestic product — two metrics that experts say give a sense of scale.

Depending on what projection of the current bill you use and what yardstick you measure it by, at least one tax bill on the Treasury list, and possibly others, were larger.

Here’s the list by inflation-adjusted dollars:

Tax bill Inflation-adjusted dollars American Taxpayer Relief Act of 2012 (enacted in 2013) $321 billion Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 $210 billion Economic Recovery Tax Act of 1981 $208 billion Current tax proposal $150 billion - $220 billion Revenue Act of 1964 $64 billion Revenue Act of 1945 $60 billion Revenue Act of 1978 Featured Fact-check Says Joe Biden “wants to put a 3% annual federal tax on your home.” $55 billion Revenue Act of 1948 $38 billion

At least the 2013 bill -- and possibly the 2010 and 1981 bills -- exceeded the current bill in inflation-adjusted tax cuts, depending on what figure you project for the current bill.

And here are the tax laws ordered from highest to lowest as a percentage of GDP:

Tax bill Percentage of GDP Economic Recovery Tax Act of 1981 2.89 percent Revenue Act of 1945 2.67 percent Revenue Act of 1948 1.87 percent American Taxpayer Relief Act of 2012 (enacted in 2013) 1.78 percent Revenue Act of 1964 1.6 percent Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 1.31 percent Current tax proposal 0.8 percent-1.2 percent Revenue Act of 1978 0.8 percent

By this measurement, at least six bills cut taxes by more than the current proposal. A seventh, the Revenue Act of 1978, is essentially tied with the current proposal as a percentage of GDP.

The Committee for a Responsible Federal Budget has noted that an even earlier tax cut, from 1921, accounted for 1.1 percent of GDP.

The group added in a blog post that "if President Trump wanted to pass a tax cut that exceeds the record 2.9 percent of the economy in 1981, it would cost roughly $6.8 trillion over ten years."

No formulation of the current proposal is close to that.

"Unless lawmakers scrap their current plans for tax reform and start over from scratch, it’s simply implausible to claim that this legislation will provide the largest tax cut in U.S. history," said Joseph J. Thorndike, director of the Tax History Project at the group Tax Analysts.

Our ruling

Trump said the GOP tax plan he is supporting is "the biggest tax cut in U.S. history."

Even the most expansive estimate for the current proposal’s tax cut is exceeded by the 1981 tax cut in inflation-adjusted dollars. And as a percentage of GDP, a half-dozen or more previous tax cuts were larger.

We rate the statement False.