@BSL
You bring up an important judgement call on priorities and imperatives. If one comes from the direction that sexual and emotional happiness is the proper context that marriage and family occurs, then your point is spot on. If one comes from the Christian perspective that marriage is the proper context of sex and family, then the comments will always talk past each other.
This leaves aside a difficult question of pragmatism, because the graphic nearly addresses the question of what kind of partner should I chose if I want to reduce my risk of divorce. This is a very serious and important question to men, being on the receiving end of the super majority of divorces.
We all know the increased risks of divorce during youth, poverty, and low education. This question of previous partner count ("N-count" for brevity) is another factor to consider that is taboo to discuss among the politically correct crowds. I say "nearly" because as Rev was quick to point out, (and I don't disagree), correlation is not causation. There are probably just as many theories as to the direction of causation as there are people who consider the questions of divorce as a function of age, economic class, education and N-count. It is for this reason that I posted the graphic without comment, because I am not convinced of anything yet on causation, but real statistically significant data is a good antidote to anecdotal experience of the original posting.
Is that graph reporting on the number of sexual partners for men, women, or both?
Women only. The chart for men is similar in trend but a reduced slope. I think that implies it is less of a leading indicator for men. The reason I think this (but haven't done the math to back it up) is imagine a couple with equal N-count, say 5. Knowing nothing else, we would say her divorce risk is ~70% +/-10%. If the guy's divorce risk is statically significantly less, I don't have the numbers in front of me, but I think its on the order of ~50%, and we know that woman initiate ~66% of divorce. So if this high risk woman initiates divorce against the guy, then he still shows up as risk impacted. Combining these 3 numbers it implies to me that the guy's N-count is much less significant. But statistically, it is still there.