Stock market is entirely irrelevant for most of Americans [2]
[1] https://www.businessinsider.com/record-median-household-inco...
[2] http://time.com/money/5054009/stock-ownership-10-percent-ric...
But if you assume that new entrants to the economy develop skills and move up over time as they acquire skills and responsibility, as is likely a closer reflection of reality, then their wages have grown over time. The observation you are making shows that for new entrants to the economy at low income levels, there has not been a net increase in the starting wages those people earn since the 1970s.
I guess the question to ask is: should we expect the real earnings of low level, low skill jobs (not people) to increase over time as the economy does? As you said, these are relatively flat. I have no reason to assume someone performing low-skilled labor in 1970 should be paid more in real terms than someone today doing the same job, in pure economic terms. For that to be true, they'd need to be performing some kind of increased value in their job relative to 40 years ago -- but if they were doing that, they wouldn't be performing a low-skilled job anymore, and hence would be moving up in income level!
80% of the country makes under $65k[1]. They're pretty locked in. This talk of "upward mobility" is not really true. Only a few will move up the chain, but not the majority. Not everyone is moving into management, not everyone is becoming a software engineer. With the costs of college education & textbooks rising exorbitantly, less people are able to afford to get the skills to move up [2].
>I guess the question to ask is: should we expect the real earnings of low level, low skill jobs (not people) to increase over time as the economy does? As you said, these are relatively flat. I have no reason to assume someone performing low-skilled labor in 1970 should be paid more in real terms than someone today doing the same job, in pure economic terms.
The cost of everything necessary is rising[2] while income's have stayed the same since the 70's when adjusted for inflation, so yes I expect "low skill" jobs to keep up. "Low skill" jobs are still a necessary part of the economy and someone hast to do them; who's going to pick up your trash at work, who's going to make your smoothies, who's going to prepare your breakfast sandwiches, who's going to pick up trash at event stadiums, who's going to cut your hair?
[1] https://www.ssa.gov/cgi-bin/netcomp.cgi?year=2016
[2] https://www.abi.org/newsroom/chart-of-the-day/price-changes-...
Do you have a citation to support these claims? A cursory search yielded a study that showed at least from 1995-2005 these claims were completely false, and the majority of people moved up from the lowest quintiles of the economy.
https://www.stlouisfed.org/publications/inside-the-vault/spr...
> The cost of everything necessary is rising[2]
If you look at your reference this is also false. Some necessities are flat, some have gone up. And most of the necessities like food and housing that have gone up, at least according to your reference, have tracked inflation so in real terms have not gone up and hence we should not feel like flat wage growth has reduced the availability of these necessities to the people who are economically immobile. And of course, in real terms, clothing and other necessities have gotten cheaper. You also gloss over that non-essential items that improve quality of life like tech have dropped radically, increasing the overall purchasing power of people within those spheres over time.
The remaining items like medical care and college education cited are cause for concern, but if we're being honest both of those areas are effectively in a state of crisis right now due to out of control costs, broken systems, and predatory lending practices. On the education front at least there is cause for hope due to the increasing availability of alternatives.
You paint a particularly bleak picture that is not backed up by your own sources, I'm afraid. That's not to say there isn't room for improvement in income mobility in the US or reducing the costs and waste in systems like healthcare, but like I said there are plenty of reasons for optimism and a belief that the trajectory is a positive one.
It is cheaper in most fields to skill up than it ever has been.
It's just more expensive to get a piece of paper....
> I expect "low skill" jobs to keep up.
Then I hope you are against all low and semi-skilled immigration.