In an analysis published on Friday, the Joint Committee on Taxation (JCT)—Congress's official scorekeeper—concluded that the final Republican tax bill doesn't come anywhere close to paying for itself and manages to be worse for the deficit and economic growth than the previous House and Senate versions.

JCT also found that, even after accounting for economic growth, the tax bill President Donald Trump just signed into law Friday will add $1.1 trillion to the federal deficit over the next decade.

JCT dynamic score just out. Shows: 1. Annual growth rate is 0.01 to 0.02 pp higher over ten years. (Yes, less than 2 hundredths of a percent.) 2. Tax cut costs $1.071T 3. Conference bill is more costly and less pro-growth than House or Senate.https://t.co/Z4hHNwXfHq — Jason Furman (@jasonfurman) December 22, 2017

JCT says that in compromising the House and Senate bills, Republicans came up with something that does less for growth and increases the deficit by more than either earlier version.



Good work all around. https://t.co/cvOqYTBj8Q — Subscribe to My Newsletter (@mattyglesias) December 22, 2017

But Republicans didn't bother to wait for the JCT's official analysis before ramming their bill through Congress. Instead, they relied on the "estimates" outlined by the Treasury Department, which claimed that the legislation would pay for itself—but only by taking into account legislation that hasn't even been proposed yet.

"Republicans spent years demanding the JCT start doing dynamic scores of tax bills," notes Vox's Matt Yglesias. "Then they decided to pass their bill before waiting for the dynamic score because they didn't like what their own analytic methods said about it."