I want a graph with the dictatorshipness on X, age of the head on Y and rationality on Z.

That would require their government to have acted rationally in the first place. The first 30+ years of economic reforms weren't done out of rationality, but one of necessity to survive as the country was on the verge of total economic collapse by the end of the Cultural Revolution. Their hands were forced in the process of keeping everyone employed and fed, which gave a sense of rationality. Even during this supposed golden era of economic liberalism, there was rampant government corruption, oppression of dissent, and censorship (that was easily permeable because the technologies and funding for total blanket surveillance weren't ready until the mid-2010s).