My commentary is this: It looks like around 1982, the trend reversed, well before the privatization. My takeaway is that whatever the government had done under nationalization was successful at addressing the concerns that existed and contributed to a downward trend that began before nationalization.
There are lots of wiggles in any graph and you can always take a wiggle and say "ah the trend was reversed". Privatization showed a steady growth in passenger numbers for decades. Nationalization didn't.
The trend is not a "wiggle." It is the slope of a local region, around which the "wiggles" bounce.
Sure, I agree: privatization continued the trend that nationalization established.
My point is simply this: the graph on its own doesn't indicate anything causal, but your original comment implied that the graph is enough to prove that privatization caused the growth.
Sure. The graph on its own doesn't prove causality. The graph, plus a little basic common sense, does give strong evidence of causality. Specifically, there's no other plausible alternative for the sudden dramatic turnaround in the mid-80s and sustained growth thereafter.
The turnaround in the mid 1980s predates privatization, so unless everyone had time machines back then, this is evidence against causality.
Also: common sense is not evidence. It never has been, nor will it ever be. Justification? Sure. Could even be that common sense is correct. But, evidence? No.
