This drives down the cost of labor. If, to make ends meet, you need two people working, they won't be able to easily move to pursue better employment unless both find employment at the same place at the same time, or that the new offer is significantly better than the previous one. As this would depress salaries everywhere, that's very unlikely.
This part of your comment was super confusing. So much so it seems better in reverse:
>As that's very unlikely, this would depress salaries everywhere.
Another thing I didn't see in that data set was the relative growth / decline of union membership; i.e. how that affected wage growth, indirect effect of negotiating power. It would also be interesting to see whether that was a leading co-factor or a following co-factor.
The way things are now in the US wasn't inevitable.
I always wonder how much of the California economic claims are due to California vs due to access to cheap overseas labor with major ports.
The massive increase of women joining the labor market in the US just after 1970 largely as a consequence of the widespread adoption of oral contraceptives in the young population. [1]
The People's Republic Of China was formally admitted to the UN in 1971, and following that in 1972 Nixon visited - effectively opening China as an actual labor market.
Edit: I think one of the major takeaways should be that, changes in worldwide monetary policy allowed for pent up demand for globalization to be realized and that accelerated shifts from onshore to offshore manufacturing. Basically it allowed the US to stop building, and start buying.
[1] https://dash.harvard.edu/bitstream/handle/1/2624453/Goldin_P...