Updated: I changed the graph to include when recessions have happened over the last 100 years. I also added a few more thoughts down at the end.

I posted the majority of this as a comment in a diary but I thought it could use a little more thought and could warrant a full diary.

There has been a lot of talk lately about the national debt; faultguy posted an interesting article that said something to the effect that the national debt to GDP ratio is on its way to be at the highest level since 1950. So I wanted to look at what were the factors that contributed to getting to this level. My main hunch was that military spending would be a large factor.

Debt-defense w rec

This graph shows the relationship between gross public debt as a percentage of GDP and Defense spending as a percentage of GDP. What stood out to me as that there seems to be more or less two different eras for the debt to GDP: 1900-1979, and 1980-2010. I have also included the recessions that are shaded in grey which correspond with some of the spikes in the national debt.

From 1900-1950: increases in Defense spending as a percentage of GDP (proxy for war spending) were positively correlated with the national debt. Changes is defense spending as a percentage of GDP explained about 51.68% of the change in national debt as a percentage of GDP over the period. This suggests that a large portion of the national debt is due to war spending. The coefficient is 2.35, which means that for every 1 percent increase in defense spending as a portion of GDP the gross national debt as a percentage of GDP increase 2.35 percent.

1900-1980: I added this and it seems to have even stronger predictive power than 1900-1950 but it still is pointing in the same direction. This has an even stronger positive correlation, and explains 53.98% of the change in national debt as a percentage of GDP. The coefficient is a little larger as well at 2.497 which means that for a 1 percent increase in defense spending it increases the national debt by about 2.497 percent.

1979-2010: This is going to blow your mind because it certainly blew mine. 1979 is the point where the gross public debt/gdp ratio is at it's lowest. It reached a point of 32.26%, so from this date to the present defense spending as a percentage of GDP is still correlated only now it is negative! The explanatory power has fallen as well to about 23.4% of the changes can be explained by defense spending as a percentage of GDO for gross national debt as a percentage of GDP.

Now this is the part that will blow your mind. For an INCREASE in defense spending it will LOWER the deficit. So the interpretation is a 1 percent increase in Defense spending as a percentage of GDP will lower the gross national debt by 6.15%!

If I were interpreting this I would say that something else became the driving factor in the National debt. When you look at the percentage of the budget dedicated to defense it has been shrinking considerably since 1900. From 1900-1970 it averaged 49.02% of government spending; from 1971-2010 it has only 27.24% of spending.

percent spend

This shows the percentage of the budget that is dedicated to defense. If we again look at the period 1980-2010 the amount going to defense is pretty flat and actually down.

After considering these factors I think that it is fairly safe to say that yes the previous high was due in a large part due to war/defense spending. We were spending 54% of our money on that category and were only 5 years removed from spending nearly 90% of the federal budget on that. Compared to now where we spend only 24% of the budget on defense (still a whole lot) and over the last 20 years it has been roughly flat with a max of 24.27% and a minimum of 19.55% with an average of 22.37%.

So something changed considerably from the last time the debt was at this level, then we spent a lot of money on a war and the debt came down as we lowered defense spending. Now defense spending is at among the lowest levels in the last 100 years (But trending upward) and we are still approaching record debt levels.

I think that it would be very hard to say that our current debt is due to fighting a war and it will return to manageable levels after the war is over and defense spending decreases like was the case after World War One/World War Two/Korea/Vietnam (even this is hard to see in the numbers but could be due to trying to accomplish having both "guns and butter" so increasing both war and other spending).  The other lines in the budget (namely Medicare and Social Security which together make up about 40% of the budget and growing) seem to have taken a diminished the importance of defense spending in relation to national debt.

So I do strongly believe that the National debt is something to worry about and that unlike the previous high's reached after World War Two where we could rapidly lower spending after the war was over this time it will not be so easy.

The solutions are not really palatable for either party. It would take large substantial cuts in entitlments and some form of tax increases.

The entitelments and other non-discretionary portions of the budget are large and growing and at the current projection can not be maintained, these need to be addressed. The likeleyhood of that any time soon is not good, as we can see we would rather kick the can down the road and make more promises on top of the ones that we can not pay.