Debt service and RGDP growth

I went to FRED for data on debt service and RGDP growth. Brought the data into Excel and showed each series along with a smoothed version using Hodrick-Prescott:

Graph #1

Debt Service (FRED's TDSP) is shown as the blue line. The thinner line, darker blue, is the smoothed version. The data frequency is quarterly, and the Hodrick-Prescott smoothing factor is 1600, standard for quarterly values.

The jiggy, dull red line shows Real GDP growth (FRED's GDPC1 as Percent Change from Year Ago). The thinner, bright red line is the smoothed version. Again, quarterly data and a smoothing factor of 1600.

My objective here is to compare the general trends of RGDP Growth and Debt Service, so on the next graph I'm keeping the smoothed lines and omitting FRED's data series. To facilitate the comparison I'm using a data manipulation technique that I picked up from Lars Christensen.

I figured the series average for the smoothed Debt Service series, and subtracted the average from each value in that series. This centers the blue line at the zero level. I did the same for the smoothed RGDP series, so both series are centered at the zero level.

Next, I figured the standard deviation for each smoothed series. I divided the relocated RGDP values by the standard deviation of the RGDP, and multiplied them by the standard deviation of the Debt Service series. This makes the amplitude of the smoothed RGDP series similar to that of the smoothed Debt Service series.

Here is the result:

Graph #2

Real GDP growth (red) shows increase when debt service is low, and decrease when debt service is high. Look for it on Graph #1 above, and you'll see it there, too. When less money is going to finance, more is left to spend on other things.

Graph #3: Household Debt Service Payments as a Percent of GDP