You know how there is currently a lot of evidence that bf-ing is linked to social class and so the so-called benefits of bf-ing attributed to the families they were born into rather than bf-ing per se. (This is just a generalisation drawn from studies but not a statement on the social class of a particular bottlefed baby, just to make things clear)
However, what I found interesting about the survery is that it followed babies over 60 years at a time when "whether or not a baby was breastfed was less to do with class than it is now, when the practice is often more popular with middle-class families. In fact, there may have been a slightly increased chance that richer families would bottle-feed babies, because they would be able to afford formula milk and nannies ... The study found there was no difference in breastfeeding rates when the researchers looked at household income or social class."
My amateur interpretation of the study is that the social climbing benefits of bf-ing seems to transcend the social class of the babies' family. So less room for the correlation, rather than the causation, argument.
Interesting. Though I agree that there are probably a lot of factors at play which, not having read the survey, need to be clarified before we can make the leap to conclude that bf-ing per se facilitates social climbing (oh dear)!