GDP growth during the last quarter of 2012 turned negative in the US (-0.1%) and this came as a surprise to many. Looking at the different components of GDP, the biggest decline happened in government spending and in net exports (due to the weakness in other economies). This is just one quarter and the data is likely to be revised later in the year, but what is to be learned from the data? The answer is whatever justifies your priors. Here is the interpretation that Larry Kudlow does in CNBC, which is a good example of how statistics can be interpreted in so many different ways.
He makes the claim that this is indeed a good quarter because private spending (consumption and investment) grew at about 3.4% - after removing inventories that fell significantly. From here he concludes:
Even with the fourth-quarter contraction, the latest GDP report shows that falling government spending can coexist with rising private economic activity. This is an important point in terms of the upcoming spending sequester. Lower federal spending, limited government, and a smaller spending-to-GDP ratio will be good for growth. The military spending plunge will not likely be repeated. But by keeping resources in private hands, rather than transferring them to the inefficient government sector, the spending sequester is actually pro-growth.
So this is an interesting test that he is using to prove that decreasing government spending is good for growth. As long as we see any growth in private spending it means that the decrease in government spending is helping the private sector grow. Of course, the real test is to compare the -0.1% to what would have happened to GDP growth if government spending had not decreased. Reading Larry Kudlow's article, it sounds as if GDP growth would have been even lower (although his statement is not as precise as this). Yes, consumption grew and investment (once we exclude inventories) grew as well, but how much? Not enough to compensate the decrease in government spending so the final outcome is a negative (literally negative) performance for GDP growth.
So if we were to use just this observation to understand the fiscal policy multiplier, what would we learn? [Just to be clear, we should not be doing this, to understand fiscal multipliers we need more than one quarter of data, but I am just trying to follow his logic.] I see that GDP growth is low and certainly much lower than what anyone would expect, taking into account that the US economy is still below potential. We see that government spending fell and this is a component of GDP. A natural reaction might be to argue that the fall in government spending had a negative effect on GDP. Given that the GDP growth number is so low (and lower than expected), this is a reason to believe that the multiplier is positive and possibly large. But, as Larry Kudlow shows, there are always other interpretations.