On the Size of those Debt Bulges

Looking at the second graph from the 25th, I wonder how the bulges got so big:

Graph #1: Public (red) and Private (blue) Debt Paths, with Path Average (dashed black)

Maybe because debt itself got so big? Let's look at the red and blue as a percent of the black:

Graph #2:Red and Blue as a Percent of their Average from the Previous Graph

Okay. The bulges are not so big now, compared to the other areas. Plus, on this graph we can see the bulge between the 1974 and 1980 recessions, and even the tiny one between the 1980 and '82 recessions.

In addition, I think I see a bulge now between the 1970 and '74 recessions. The blue and red lines didn't come together for the 1970 recession, but that doesn't mean there's no bulge after it.

So apparently the growth of debt in general has something to do with the size of the bulges. But that's not the only factor, because bulge size still varies. What could it be?

I'd like to say vigor, it's a measure of vigor, but that seems quite obviously wrong.

Hey, know what I just noticed? Look at just the blue line: It reminds me of the private-to-public debt ratio:

Figure 3: Non-Federal Debt relative to the Federal Debt