I wonder though, if the common interpretation, that the Supreme Court is in an unusual decline, suffers from systemic bias.

It appears to me that there are at least three ways the graph can be viewed.

The first is that this is a global minima based on two cycles. Whether this is a significant minimum (between the two data points we have) is difficult (I’d argue that there’s not enough data).

The second view is that we have an initial state decline after 1926 that bottoms out in 1953 and then
begins a cycle with an upsurge in the 70′s and 80′s and an decline in the 90′s and 00′s.

The third view, assuming the curve is not influenced by initial conditions is that we have a periodic cycle.

Each viewpoint likely results in a different question.

1. Why are we having a global minimum? Is this minimum mathematically significant compared with the first cycle?

2. Why was there a bubble in the 70′s and 80′s? Why a local maximum? This assumes that the low numbers from the 50-60′s and 90-00′s is the normal system state and that the 70-80′s is the abnormality.

3. Why is the case load sinusoidal? That is, why is it periodic?

Otherwise the question posed is why is any specific year higher (or lower) than any other year? Which is difficult to answer using statistical methods.