“Tax grade” part II

Ever since my brother developed the concept of “tax grade” to explain Stephen F. Hayward’s rankings of the presidents from Wilson to Obama (and his presumptive high ranking of Trump), I have had a look at Hayward’s grades and found some interesting patterns in the grades over time, as can be seen from the following graph:

This graph – with two grades between each grey line – illustrates the “constitutional grade” (higher grade being shown higher on the graph) of United States presidents between 1913 and 2017 according to Stephen F. Hayward’s The Politically Incorrect Guide to the Presidents: From Wilson to Obama.

 What I noticed on close examination is that:

1. of the theoretically possible “constitutional grades” from A+ to F, only seven are actually given by Hayward to any president between 1913 and 2017
2. the possible grades not given by Hayward to any president are:
1. A
2. B-
3. C
   
4. D, D+ or D-
5. E, E+ or E-
3. all grades higher than B minus (as I noted no president received a B- from Hayward) occur before 1930 or after 1980
4. all grades of C plus or C minus (there is no straight C as I noted) occur between 1930 and 1980
5. between 1930 and 1980, there is some overlap between Republican and Democratic presidents, although every failing grade is still given to Democrats Roosevelt, Johnson and Carter
6. contrariwise, before 1930 and after 1980, all Democratic presidents get failing grades, and all Republican presidents receive grades of B or higher

My brother believes that this difference occurs because before 1930 and after 1980 there was little acceptance by the US ruling class of the idea that taxing the super-rich was legitimate, and that the Politically Incorrect Guides are entirely about eliminating taxes on the super-rich. Whilst I appreciate my brother’s comments, I do see flaws.