This was a really interesting read, thank you for laying it out.
Are PDFs like that Direct Democracy common releases from the UK parties? It really spells things out, at least as far as I made it through before getting distracted.
There did seem to be a couple sections that I read that the data didn’t seem to match what was being claimed. Particularly the section on the Broken Pendulum (Pages 8,9). The authors seem to claim that in 2001 and 2005 were unique in that the opposition party wasn’t able to gain from losses in the government. If however you look at 1964 and 1983 they seem to be even more stark examples of the same. Seems like the pendulum was a general trend at best.