I don't remember looking at this before

I got RGDP growth rate data from FRED and put a Hodrick-Prescott on it. Then I put a linear trend on it. Two linear trend lines, actually: one based on start-of-data thru 1980, the other based on the post-1980 period:

Both linear trend lines run from start to finish on the graph. But the lower one is based on the data from 1947 to 1980. The upper one, the dashed black line that starts at or above the 5% level, is based on data that starts in 1981 and runs to 2019.

The dashed line is higher at the start. But this doesn't mean growth was better under post-1980 policies. It means growth was going downhill faster under the post-1980 policies than under the pre-1980 policies.

What I find interesting on this graph? Two points:

1. Growth was slowing in the early period, almost as much as it was slowing in the latter period.
2. Both trend lines end up in the same place. Same result either way.

I won't dwell on these points, but you might want to think about them.