the CBO can only project via the numbers they are given.......which is why the numbers for Obamacare were cooked in a pressure cooker and exploded. The CBO was lied to.
It's been shown numerous times that dynamic scoring is actually closer to the truth than any 'guesswork' or 'hoping' by people like Gruber would put forth. All growth is hypthothetical....it's built around hopes and not reality, unless you know the 'truth' ahead of time and lie to the CBO in order to get the results you want from that agency.
As for Bernie Sanders.....he's an admitted Socialist and will probably run for president in 2016....I wouldn't give him much credibility now that BO's socialistic agenda has failed miserably. They all want the same thing and it doesn't work.
Bernie Sanders Blasts Paul Ryan and House Republicans For Trying To Cook The Books
The Republicans have hatched a plan to force the CBO to cook the books and paint a rosy picture of the benefits of trickle-down economics. They call it 'dynamic scoring.' In fact, it's a gimmick to help justify more tax cuts for the wealthy and profitable corporations. It's what the first President Bush called voodoo economics - and he was right.
The purpose of dynamic scoring is to conceal - not reveal - how Republican policies will affect the economy.
The basic problem with what the right-wing economists call "dynamic scoring" is that it requires the CBO to count hypothetical growth as additional revenue. "That means counting the chickens before they hatch.