It will be interesting to see whether his study can be replicated in comparison to Singapore.
It appears that he seems to be corelating relative changes (up or down) in democracy in each individual country to its economic performance but not the absolute political freedoms between the two countries themselves.
The argument that India is showing poorer economic growth is because it has regressed in terms of democratic freedoms between 1961 - 1991. and that China is showing greater economic growth because it is slowly improving and reforming its local-level politics (villages) seem a little shaky. I’m not totally convinced.
China and India doesn’t seem to be a good comparison because both countries started from a very different political level. India inherited democracy, China on the other hand came out of absolute monarchy.
Perhaps, a study could be done comparing Singapore and Malaysia. Both started almost at the same level democratically (inherited from the British) and continued on for a long period of time until 2001 where both countries diverged in terms of political dynamism.
Malaysia with its opposition success and civil society pressure in 2008, when compared to Singapore at that time period would make a very interesting study.