Also, I never claimed it was a complete picture of what causes poverty. I claimed it was one possible cause of the correlation between parent and child poverty. This debunks Bowle's claim that a correlation between parent and child poverty implies hard work could not be a cause of poverty. It may or may not be, but his statistic proves absolutely nothing unless he can also show that laziness is not hereditary. Other things, e.g. bad luck, might also cause poverty, but would not be correlated between parent and child.
Incidentally, the same research about why I might prefer a "hard work" theory also shows why you would emotionally prefer a "it's not their fault" theory. My reasoning signals to my tribe that I'm hard working, and raises my status. Your reasoning signals you are caring, and raises your status. How clever, and probably true. (Except of course for the fact that I'm a member of your tribe and expressing my opinion lowers my status. But hey, I'm a sucker for statistics.)
Regarding what feels good to say.. my reasoning signals an appreciation for all the advantages I've had, and an acknowledgement that I'm really not that special, I only had to be moderately smart and hard-working given the opportunities I've had. Take my deviation from the mean and put me in the ghetto, I'm not "climbing the ladder through free enterprise and hard work". You might be more special than me, I don't know.
Hint: it doesn't. Most of it is inconclusive, and I've seen almost nothing proving hard work is not a significant factor. Regardless, my main point is that Bowle's statistic is consistent with laziness causing heritable poverty, which completely disproves his point.
As far as income mobility goes, I don't know of any research that can conclusively identify causative factors. We know whatever factors prevent mobility are heritable, location based and ethnicity based. We also they are not money/income based, since many low income immigrant groups have extremely high mobility. Vietnamese immigrants went from illiterate peasant to middle class Americans in one generation.
My first gf is a perfect illustration: in 10 years, she went from illiterate African refugee to Republican campaigner/fund raiser making more money than me (that might have changed in recent years). If she could do it, basically any American could do it.
Citing "laziness" is really the easy way out -- clearly your job and my job are more "lazy" in some senses than being, say, a day laborer. So why can't the day laborer move up easily? A whole bunch of reasons, very few of which have to do with laziness. You can try to cite intellectual laziness if you want, but these guys didn't exactly get a chance to take AP calc senior year.
Regarding your ex, yeah, immigrant groups do have extremely high mobility and that's one of the great things about America is our (waning) receptiveness towards immigrants. But they're an extremely self-selecting group. That's not "average".
Regarding you and me (assuming you're a reasonably successful developer in some fashion), the major financial differentiator between us and our peers is the fact that tech work pays really well right now and doesn't necessitate a bunch of grad school debt. If I wasn't born on an automatic trajectory for college? And was the same guy in every other way? I'm at best a 50% shot at becoming a developer.. probably I'm working at Safeway instead. And doing a good job at that job, because I'm not lazy and that's my nature.
You can claim to be substantially more "fit" than me if you want.. and hey, maybe you are -- but if you're going to claim "gumption" as opposed to "born lucky" as the major reason you are where you are, then statistically, you're probably just underestimating the luck.
If you and I work full time, we both work harder than 90% of the poor. 80% of the poor spent less than 27 weeks working or searching for a job in 2008. Another 10% of them worked only part time for more than 27 weeks/year. Less than 10% of the poor either worked or searched for full time work for 50 weeks/year. (See my previous citation.)
But they're an extremely self-selecting group. That's not "average".
So basically, you are saying a group of people who are self-selected to be hardworking and show initiative [1] can break out of poverty? And they do this in spite of having low income, little access to credit/finance/consumer banking, a quality education, or even the ability to speak english?
That pretty much proves that low income, little access to consumer finance and lack of a quality education do not prevent a hardworking person from breaking out of poverty. This is evidence for my hypothesis, not yours.
[1] In some cases, they are simply self-selected to be fast runners, good at hiding, or other such non-marketable skills. See, e.g., Vietnamese, Somalian or Igbo refugees, all of whom exhibit greater income mobility than poor Americans.
Let's go back to my safeway example. If I don't grow up in an environment where it's assumed I'm going to be college-track, I probably work at safeway. Working hard isn't all I need at that point -- my ceiling is "shift supervisor".
I'm a big fan of the outlier theory or the "2% theory" as I used to call it, 2% of people tend to make their own destiny, you put them anywhere and they'll become ambitious and try to do things. Most people don't, including most people who aren't in poverty. How many friends do you have who went to law school because, "I dunno, I'm not gonna work at Safeway the rest of my life?"
There's also a lot of research out there about why you would prefer that line of reasoning you expressed, and would argue it in order to feel good about yourself.