Department of "Huh?!" Greg Mankiw Is Not Making Any Sense...

The $787 billion ARRA was about 2/3 spending increases and 1/3 tax cuts. Jared Bernstein and Christie Romer estimated that with a spending multiplier of 1.57 and a tax multiplier of 0.99 that the ARRA would boost production over its lifetime by $787 x 2/3 x 1.57 + $787 x 1/3 x 0.99 = $1,083 billion.

Now comes Greg Mankiw to say that they overestimated the impact of the ARRA because their multipliers were wrong: that he prefers a tax multiplier of 3 (from Romer and Romer) and a spending...