Hence why I also provided personal income, but both data points show a significant correlation between dual-income households since the 1980s, so that is a moot point.

Also, as at this point 1980 is 45 years ago - almost 2 generations, almost like using the 1960s as a frame of reference in 2005.

At this point we've been a country of dual earners in a household for 2 generations now. It's best to assume that is the default given the overlap.