statistics
I have to agree with Daikilo.
Another thing to bear in mind is where the aircraft fly. There is sure to be a correlation between the country where the aircraft are maintained, where their pilots are trained, and the quality of the airfields the planes fly from.
In the '70s, the vast majority of 737s were likely flying in first-world countries. A fair fraction of the rest of the world was flying russian-built aircraft. As other nations have developed somewhat and the USSR disintigrated, we're seeing a lot more jets flying in less developed countries. So you can't simply compare total stats across 40 years - it's an apples to oranges comparison.
You might be able to compare stats for the same time period, but you'd only get a reasonable comparison if you normalized for other factors. For example, you might get a vaguely fair comparison if you compare aircraft flying for US-based airlines, because they will be flying more similar routes and have more similar maintenance procedures.
- Fzz