Suppose the abstract of a paper starts with "It is demonstrated that the US economy has on the long-term in reality been governed by the Keynesian approach to economics independent of the current official economical policy." My first reaction is that of puzzlement, as I would not have thought as the US being particularly keen on Keynesian policy, except for the recent years (which are not considered in the quoted study). But again, data may speak differently from policy intentions, so let us dig deeper.
A. (Agung?) Johansen and Ingve Simonsen come to this stunning conclusion by looking at the correlation between (nominal?) (federal?) public debt and the Dow Jones Industrial Average. One can first question whether public debt is a good indicator of Keynesian policy. Public deficits or even public expenses would be better. And does the DJIA represent the US economy? It is certainly not an indicator of current activity, but rather of expected present value of future profits from a particular class of firms.
Whatever. Let us go with that. The analysis is done by computing over the 1791-2000 sample a sliding correlation between these two indicators over a five-year window. Surprise, the correlation is zero most of the time, except during some wars when it is strongly positive (and strongly negative during the second war with the Seminole Indians). From this they conclude the Keynesian policy was mostly pursued during wars. Now let us take a step back: the authors show that there is by their definition no Keynesian policy during peacetime. But during wartime, the government is credited with a policy geared towards expansion of the DJIA. They, one may ask, if this is the government overwhelming policy, as the authors seem to believe, why did the US wait so long to get into the two World Wars when the opportunity was there? I cannot make sense of all this.