Also, I think our society should still be structured to allow a single earner on minimum wage to support a family of four, without going on welfare of sorts. It's really complicated though, and for every argument supporting one side of this argument you can always find a really good rebuttal.
How could society be structured to guarantee higher wages to unskilled workers?
What you just described is a family of 4 with a total income of $30k+.
Per capita GDP of $45k means that GDP per 4 people is $180k. That $45k number is per person, not per worker.
So either the claim is that $30k is not that bad compared to $180k (unclear, a priori) or ... something?
http://en.wikipedia.org/wiki/Household_income_in_the_United_...
I agree that household income is a more interesting thing to compare to for this case, though, but even more interesting would be comparing to similar households. Otherwise you're comparing the income of our hypothetical family of 4 to the incomes of 1-person households, incomes of households containing just a student, incomes of households containing one or two retirees, and so forth.
Luckily for us, such information is out there; http://www.census.gov/hhes/www/income/data/statistics/4perso... lists the median family-of-four income in the US at $67,000 or so in 2005 (though by state the median ranges from about $50k to about $90k, which shows the problem with talking about aggregate "United States" numbers). http://www.census.gov/hhes/www/income/data/Fam_Inc_SizeofFam... has similar numbers for a few years later... http://www.census.gov/hhes/www/income/data/historical/househ... has quite a bit higher numbers than that for 2011 ($75k median nationally), which is a bit surprising to me, actually.
None of which answers the question of how reasonable an income of $30k is for a family of 4, of course.
Unless I have been grossly mislead, if singer-earner salaries had appreciated like CEO salaries from the 1950's to now one parent could afford to stay home or just work part time. I don't know why it should be necessary for both persons of a marriage to work full-time on average.
There are always going to be shit jobs meant for teenagers that pay wages good for teenagers (cashiers, part-time lifeguards, sandwich assemblers, etc). If an adult tries to support 3 other people with such a job, they are going to have a very difficult time and that should not surprise or disturb us.
You aren't going to get companies to scale their pay based on what the individual employee needs. If you did, would McDonalds have to pay the fry chef with 7 kids more than the fry chef with 3 kids, who is in turn paid more than the 19 year old fry chef who is trying to pay for community college and car insurance? That would be absurd. If you think that somebody needs to take up the slack, you need to look to government, not corporations.
As women entered the workforce, this created more supply, which drove wages down, which forced more women to enter the workforce. Similarly, two-earner households could outbid single-earner households when purchasing real estate, which also drove the need for a two-earner household.
This transition is not reversible. However, it only happens once (excepting polygamy).