He points out that the differing inflation regimes had a profound influence on the shape of the curve - which they do. But even with inflation out of the picture, there is still a regime change, and it still happens in the early 80's. To take away the inflation effect, I've made what I hope is a similar graph. The GDP change line is color coded by President's Party, Blue for Dems and Red for Rethugs.
I've also included a 13 year average line in yellow, to smooth out the long term trend. This clearly shows the two regimes, and when the change occurred. Here, in a nutshell, is the Great Stagnation, brought to you by Reagan, Bush and Shrub. I'm not a big Bill Clinton fan, but that dismal competition makes him look awfully good.
I'm not sure I used the same methodology as Steve. I went to FRED, downloaded series GDPC96: Real GDP, quarterly data. I then 1) took a five year (20 Q) average of the data, and 2) computed a percentage change from 4 quarters earlier for that average, for each quarter, starting in Q1 1952. This percentage change is plotted as the red/blue line. The yellow line is simply a 13 year (52 Q) average of that rate of change. Note that with the exception of B. Hoover Obama, having a Dem Pres does pretty wonderful things for GDP growth. In contrast, having a Rethug Pres means taking giant steps toward economic stagnation. I hope you knew that.
From 1970 through Q1 1981, the 13-Yr. average hovers between
Note also that the two big drops are at the starts of the Reagan and Shrub administrations. This is hardly a coincidence.