Utgangspunktet er dette:
A major question facing many governments in the rich world today is whether we should try to stimulate the economy by increasing government spending. The professional opinion of economists regarding this question is sharply divided. While many economists believe that increases in government spending can have large ‘multiplier’ effects – ie increase output by more than the increase in spending – many others are sceptical of this and some even believe that increases in government spending may harm the recovery.
Hva som gjør dette spørsmålet interessant er tiden vi lever i. Effekten av finanspolitikk er ofte vanskelig å måle. Det hele koker ned til et korrelasjon/kausalitetsproblem. To forskere, Emi Nakamura og Jón Steinsson, forsøker å identifisere et ‘naturlig’ eksperiment, hvilket kan fortelle deg mer om kausalitet av finanspolitikk mens korrelasjonseffekter blir mindre viktig per definisjon.
Hva er dette ‘naturlige’ eksperimentet? Jo, krigsutgifter fordelt på forskjellige stater i USA.
We use the fact that when the US embarks upon a military buildup, there is a systematic tendency for spending to increase more in some states than others. For example, when aggregate military spending in the US rises by 1% of GDP, military spending in California on average rises by about 3% of California GDP, while military spending in Illinois rises by only about 0.5% of Illinois GDP. Under the assumption that the US doesn’t embark upon military buildups like the Vietnam War because states like California are doing badly relative to states like Illinois, we can use regional variation associated with these buildups to estimate the effect of a relative increase in spending on relative output. Our conclusion is that when relative spending in a state increases by 1% of GDP, relative state GDP rises by 1.5%.
Ser du hva som skjedde? Ved å se på forskjeller mellom regioner/stater, klarer forfatterne Steinsson og Nakamura å spytte ut en multiplikator på 1,5.
Så hva med pengepolitikk. Hvordan vil sentralbanksjefer med allerede lav rente respondere til en tiltakspakke? Forfatterne argumenterer:
An important special feature of the current situation in many economies is that nominal interest rates are very close to their lower bound of zero. This constraint implies that nominal interest rates are likely higher at the moment than the monetary authorities in these countries would like them to be. This means that these central banks are unlikely to respond to fiscal stimulus by raising rates the way they would in normal times. In other words, monetary policy is likely to be more accommodative in response to fiscal stimulus today than in normal times.
It turns out that our analysis is particularly well suited to help us draw inference about this situation. As we discuss above, we know from the fact that the US is a monetary and fiscal union that the Fed can’t differentially increase interest rates in one region versus another and that Congress doesn’t raise tax rates in one region relative to another. This pins down an important ‘moving part’ when it comes to interpreting our estimate of the fiscal multiplier.
Modellen (pdf) er helt etter boka, og resultatene støtter multiplikatorliteraturen.