For people who want an impartial survey of multipliers, see Patrick Van Brusselen, “Fiscal Stabilisation Plans and the Outlook for the World Economy”. It’s a useful antidote to the blogposts that cherry-pick multipliers from a given model to make a given point. The survey ranges over US, euro-area, and Japan; and structural macroeconometric models, DSGEs, and VARs.
The paper also takes a longer run perspective.
Figure 4 from Patrick Van Brusselen, “Fiscal Stabilisation Plans and the Outlook for the World Economy” NIME POLICY BRIEF
01‐2009 (Federal Planning Bureau, April 2009).
Figure 4 suggests lots of opportunity for econometric testing for trend breaks, difference stationarity and trend stationarity. For some of the reasons of why that debate would be relevant, see here and here.