Odd that the graph shows how much better the average family is off than in 1960, 60 years ago. As the graph shows, 1960 to 1970 was the largest boost. And most of the family income boost from 1970 to now was due to the wife having to work, not higher wages.
Not the case for Google L6s, but the economics of the majority of US workers.
With dual income you have to pay for daycare (2-3k/month), and that's not pre-tax. This lead to less births, requiring more immigration. The government used illegal immigration to fill the gap, which has put strain on our social services such-as schools.
I wonder if we were better off economically with the single earning household norm.
What probably happened is women having opportunity other than having kids and being a housewife brought out the costs of having kids that women were previously eating on behalf of society. Now the costs are more explicitly and society needs to pony up to make it more attractive.