If you could measure what would have happened if parents stayed together then yes. But parents break up for a reason, and trying to put that back together makes

If you could measure what would have happened if parents stayed together then yes. But parents break up for a reason, and trying to put that back together makes zero sense. In the US, a large minority of single parents have fathers who have spent time in jail...is it a good idea to put a child into that environment? Probably not. And the main issue with single parents is income/income instability (which is why there are focused benefits in many countries for single parents). As ever, an income issue gets classed as something else.