The book is for fun: it's not a rigid scientific approach. I really enjoyed that book. The main point is that these successful people are primarily entrepreneurs. Also that it's what you keep, not what you earn. I know plenty of people with higher incomes than I've ever had who have few assets to show for it. They probably think I'm poor, living in my little 3000-square foot home and driving a 5-yr-old car. I'd much rather have assets in the markets than in the garage. I don't care what other people think. Trading is an entrepreneurial business-you are working for yourself, right? BTW, it absolutely is possible to become a millionaire/multimillionaire in the markets. It just takes a while. I was lucky to get started in 1987 at the beginning of a great bull run (after the nasty 1987 hiccup, of course). You gotta keep at it fervently--keep your eye on the ball. It won't work if you have an excessive number of children or pull $50K+ out every couple of years for a flashy new vehicle. It's kind of like going to the gym. You can have the results you want if you apply yourself consistently over a long period of time, but you will never get there if you are also washing a 16-oz ribeye down with a few glasses of Scotch twice a week.
A literal interpretation of this book is of little value. The main point is saving money is more important than income in determining future wealth for the average (if not majority) of people. It is a financial adaptation of the old adage "slow and steady wins the race." Ignore the advice at your own peril. I've seen so many traders make more money than me who now own nothing or worse -- are deep in debt and out of the business. While I live slightly below my means and now have a ton to show for it. Not to mention a bankroll to support myself through tough trading times. In this business you need to save for a rainy day. Being a career trader requires an absolute commitment. Saving for bad trading is part of that. There are other ways, but this is one realistic system that most people can use to increase the odds of a comfortable future. Good luck to all in your quest!
lets see - how about France, Germany, Sweden, Canada, Finland, Norway, Denmark based on this study: https://www.brookings.edu/wp-content/uploads/2016/07/02_economic_mobility_sawhill_ch3.pdf More or less the same is said in this study, though their methodology is somewhat different: https://www.oecd.org/eco/growth/NER...ality-social-mobility-and-economic-growth.pdf
But not really, there are many separate messages in the book. The "live below your means" one is prominent but secondary. It's also one of the few bits there that show some statistical significance and common sense. However, what I think is the main message, that "any blue collar worker cab become a millionaire if he/she follows this recipe" is largely (if not fully) crock of shit.
As someone who use to study this stuff, data is very messy and in dealing with anything in the US, even more so. The studies you cited said that upward mobility is about the same in the US as most of Europe when we start at their working life not at birth. So yes, once one is of the working age, their rate of growth is on par with other countries in Europe. The problem in the US is the starting point. If you are born into poverty you have a challenging road ahead. Not a real shocker there. Also, debt plays a big role. If your parents are poor and debt burden then upon their passing, they may have little to nothing to hand down to their kids. This is a huge issue especially with minorities in the US. This data is very complicated and it's best not to make broad generalizations. As the old saying goes with data, "if you torture it enough, you can make it say anything you want."
Maybe we are reading different papers or something. Both studies that I linked more or less talk about the same thing - intergenerational economic mobility as evidenced by income plasticity in one or another form (another, a more comprehensive study can be found here: https://inequality.stanford.edu/sites/default/files/Pathways-SOTU-2016-Economic-Mobility-3.pdf). There is nothing in these studies (at least that I can see) that looks at the intra-generational mobility at all. While yes, you can tweak the data, I think these conclusions (which, I guess, you agree with) are pretty sound.