A good deal of the products the CBO develops are "forward looking." If the Congress does X it is likely to have Y (and perhaps Z) results.
This is in contrast to many Executive Branch institutions, like the Bureau of Labor Statistics, that report on the effects of programs and policies already in place.
The BLS is the organization located within the Department of Labor that analyzes employment data and reports the unemployment report that is breathlessly awaited on the first Friday of each month.
It is a matter of Washington lore that if these agencies' reports reflect your political view, they were prepared by the modern equivalent of economic saints in white robes, and are truthful, accurate and prove your point.
If, on the other hand, they do not reflect your political view then they were prepared by a bunch of drunks and interns (I recognize that is a redundancy) who are operating at the behest of your political opponents and their output is not worth the thumb drive it was copied to.
A most egregious example of this was the aforementioned Richard Nixon, who according to Woodward and Bernstein in "The Final Days" via the Washington Post:
"became obsessed with the idea that a 'Jewish cabal' at BLS was undermining him by issuing negative labor numbers. Nixon ordered his subordinates to tally up the number of Democrats and Jews in the agency."
As to the latest CBO estimate of jobs and the minimum wage, the White House trotted out the Chairman of the White House Council of Economic Advisors whose best response was: "Zero is a perfectly reasonable estimate of the impact of the minimum wage on employment."
I had an Econ professor who used to say that if you laid all the economists in the world end-to-end they still wouldn't reach a conclusion.
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