Does the size of a country's national debt with respect to the size of its economy affect its economic growth prospects?
To find out, we created the following chart showing a relationship between the inflation-adjusted economic growth rates for the member nations of the Organization of Economic Cooperation and Development (OECD) against their "publically-held" debt-to-GDP ratios in 2011:
What we see is that high levels of national debt with respect to the size of a nation's economy, would appear to have a medium-strength effect upon its real rate of economic growth. For every 10% increase in a country's national debt with respect to its GDP, it would appear that its real economic growth rate is reduced on average by roughly 3/8th of a percent. A 26% increase in a nation's debt-to-GDP ratio then would coincide with the shaving of a full percent off its real GDP growth rate.
That matters because economic growth is exponential. A nation whose economy grows at an average rate of 3% per year will double in size in roughly 24 years. A nation whose economy grows a full percent less than that at an average rate of 2% per year will take 36 years to double in size. The difference between the two growth rates is very noticeable.
Looking at the United States' position on the chart, we note that the debt indicated in the chart applies only to the "publically-held" portion of its national debt - if we included the "intragovernmental" portion of its national debt, as would represent a more correct accounting of how much money the U.S. government has really borrowed, it would be over 100% of GDP in 2011.
CIA World Factbook. Country Comparison: Public Debt. Accessed 27 May 2012.
CIA World Factbook. Country Comparison: GDP - Real Growth Rate. Accessed 27 May 2012.