In my time going to college I have not felt that "rational, liberal thought" is in contrast to any perceived "dogma" that I have been taught as one of Jehovah's Witnesses.
Also remember that the chart statistics only use income as a measure of comparison. This is fairly meaningless because lower income does not necessarily mean a worse living condition or less happiness.
I left at 18 when I discovered that evolution wasn't the nonsense I'd always been taught. There was a period where I searched desperately for any credible arguments against it, and found none. When I started talking to the people who had been telling me it was wrong, I realized that they had no idea what evolution actually was. In some cases, they didn't know the distinction between natural selection and the theories of the origin of the universe.
People accuse the JW's of being a cult with good reason: members are discouraged from associating with non-members. They're also told to avoid all contact with anyone who is 'disfellowshipped' (thrown out).
This means that the penalty for disagreement with the church is losing everyone you care about. 'Shunning' is a tactic very common to cults.
This also means the price for being intellectually honest with yourself is very high. That's how smart people manage to continue believing in something so demonstrably false. For me to give up my faith, strong evidence wasn't enough - it took overwhelming evidence, and even then it was a very emotionally trying time.
The reason their income is low is simple: the church has noticed that education is anti-correlated with membership and so they continually discourage it. Very much like a corrupt government tries to bury information injurious to itself.
I agree, only comparing income is rather misleading.
JW's don't smoke or do drugs and so have a far smaller problem with addictions which require professional help and counseling. So although on paper the JWs and the Black Protestant Churches look similar in terms of income one has to remember that the Black Churches have a significant problem with addiction to drugs and alcohol among their members which contributes to their low income scores.
Not smoking or doing drugs frees up more of the JWs disposable income, and the same goes for Mormons not drinking alcohol.
Also many JWs have a lower income because many of them only work part-time by choice so that they have more spare time for preaching, a by-product of this is that voluntarily being able to spend less time at work generally means less stress in the family and more time with the children.
Then again, rich man, heaven, all that jazz. We'll see who has the last laugh. Or we won't. Let's eat.
Despite calls for reform, college attendance for youngsters is still actively discouraged in favor of trade school and worse options (such as homeschooling). All in the name of being able to dedicate greater time evangelizing. All of us that have left know that the underlying rationale is to prevent young JWs from being exposed to rational, liberal thought that almost inevitably destroys their house of cards dogma.
Yes I'm smiling too. The moral upbringing was good. The emotional baggage is not.