It isn’t a 50% divorce rate and it isn’t 80% of divorces being filed by women.
I believe the real numbers are something like 40% and 69% (with substantially better divorced numbers depending on demographics). Interestingly, the percentage filed by women is very similar in a variety of times and places.
"Social scientists have known for decades that women are more likely than men to initiate a divorce. In 1956, sociologist William Goode discovered that, among couples in Detroit who’d gotten divorced in the 1940s, the wife had instigated about two-thirds of the breakups.
“Since then — in spite of shifts in gender relations, advances in women’s rights and profound changes in our attitude towards marriage itself — that finding has been replicated repeatedly, in different contexts and cultures; researchers have found the same pattern to be true in Europe and Australia.”
nytlive.nytimes.com/womenintheworld/2015/08/24/why-women-are-more-likely-than-men-to-initiate-a-divorce/