[ACow_Adonis]

we have a concept in welfare and income stats called equivalisation.

this is where we try to control for the positive material externalities that come from sharing resources among people. you dont have to buy two of everything if you share, it's cheaper to add a room than obtain a whole house and duplicate bathrooms + kitchens etc.

widows would fall afoul of this (in the sense that they've lived with that advantage for most of their lives), as well as obtain a likely wealth effect from inheritance, but it wouldn't surprise me if the entirity or majority of the marriage effect is largely just a restatement of equivalisation + social transfers/safety nets.

[achenet]

I think that having two adult role models to give a child love, and to serve as an example of 'how to have good interactions with others' is also quite important.

I was a child of divorce, and honestly it was a bit traumatizing. My parents were (and still are) often quite angry, mean and dishonest. They spent literally over $100,000 on legal fees, but "didn't have the money" to buy me a guitar.

So despite being (relatively) well off, coming from a violent, if not outright abusive at times household, suffering from parental neglect... yeah honestly that may have contributed to things like "skipping class to do drugs".

I think there's a lot of socializing that can happen in a functional two parent household that doesn't happen in single parent households, and this may be an additional advantage, in addition to equivalisation + social transfers/safety nets.

Plus as previous comments have said, if your parent has the trait "functional, responsible adult capable of having healthy relationships", that probably really increases your outcomes.

[seec]

My experience is similar to yours, especially the mean and dishonest part; your parents did not have money for a guitar, mine did not have money to pay for university. The worst is that since they were both way above the income level needed to have government support (grant/scholarship, access to subsidized housing, etc) the only way I could have done it was to leave my parents as soon as I got adult age (emancipation). They still give little care about what we do (I have younger brother) and still shit on each other and are still very much fighting with money. I learned the other day that almost 20 years lates they are still fighting for the split of 75K with another 75K in unresolved state. I think we really ought to have laws that make people pay for their children if they separate. Like a untouchable fund that has to be filled up depending on the income level of the parents and that can be used later on to fund studies or life starting costs. To be honest I think my father would have made the right thing, but it is my mother who orchestrated the whole thing and left us to rot after leaving will all the stuff plus all the money. It is extremely unpopular opinion but my experience tell me that women shouldn't be allowed so much latitude considering all little real responsibility they are given and how little social cost they will have to pay for it...