AdamT just posted what she said ... Here, read it again.
Originally Posted by Conservative
"It should be understood that all of the estimates presented in this memo are subject to significant margins of error. There is the more fundamental uncertainty that comes with any estimate of the effects of a program. Our estimates of economic relationships and rules of thumb are derived from historical experience and so will not apply exactly in any given episode. Furthermore, the uncertainty is surely higher than normal now because the current recession is unusual both in its fundamental causes and its severity."
You should be familiar with it by now, this is not the first time this has been shown to you.