I don't know how well it generalizes outside the US, but here, I would expect the correlation between happiness and ideology to reflect the fact that the political right effectively employs the just world fallacy in far more explicit ways than the political left. More advocacy of wealth redistribution is correlated with thinking that the status quo distribution is unfair. Plus, In the US specifically, both old-fashioned Calvinist determinism and modern prosperity gospelism are associated more with the right than the left.
People who think either or both of "the status quo is better than the alternative" or "it'll all even out in the afterlife" are likely to be happier than people who think the world as it is is unjust.
I've noticed a depressive tendency on the left, but I think it might be an accidental bad strategy.
Please take this as my observations which may be shaped by what I choose to read.
It seems to me that left wingers have a habit of having every bad thing in the world remind them of every other bad thing. This may be a lack of respect for specialization, or it may be a side effect of competition for mind space, where everyone is trying to recruit everyone else for their preferred cause.
I also think that efforts to puncture grandiosity have overshot to the poi...
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