Robert Barro and Charles Redlick wrote an op-ed in WSJ (link) on their original paper (link) where they discuss the macroeconomic effects of fiscal stimulus and construct long-term time-series on U.S macroeconomic data to examine whether real GDP increases follows the spending multipliers and whether reductions in marginal tax rates, rather than spending increases, tend to exert a stronger effect on GDP growth.

“Our research also shows that greater weakness in the economy raises the estimated multiplier: It increases by around 0.1 for each two percentage points by which the unemployment rate exceeds its long-run median of 5.6%. Thus the estimated multiplier reaches 1.0 when the unemployment rate gets to about 12% … For data that start in 1950, we estimate that a one-percentage-point cut in the average marginal tax rate raises the following year’s GDP growth rate by around 0.6% per year. However, this effect is harder to pin down over longer periods that include the world wars and the Great Depression.”

Rok Spruk is a supply-side economist and a libertarian.
He (currently) lives in Slovenia where he studies economics
and business. His fields of research are economic growth,
macroeconomics, international economy, global competitiveness,
and tax reforms. His views, observations and ideas are posted
on his blog.