The problem with the this assessment of a majority is that a lot of modern "developed" and mostly European societies come from a tangled and incestuous colonial origin. While culturally the origins of many modern societies may differ they are in many ways structurally very similar. This wasn't however because of a mass convergence on the best way to exist but rather the process of structure being grafted from one successful power from another.
To your point about quantitative data the main issues with a lot of this is that the prospect of generating clear quantitative data on massive society wide shifts is naive. While it's possible some numerical data does exist when looking back on the past quantifying these sorts of things become increasingly difficult. Not to mention the inherent issues surrounding the reality that quantitative data is not implicitly more reliable as the methods of data collection and presentation are heavily biased by the people involved in the research. This can lead to wildly incorrect claims being generated from "good data" that has been validated to be reliable.
TL;DR (for this last paragraph) I think you are overemphasizing the value of quantitative data as objective measure.
> I think you are overemphasizing the value of > quantitative data as objective measure.
Damn those pesky engineering courses I took in college! :-)