There’s a problem with using this metric as a measure of market health/fairness, however. As income distribution becomes more skewed toward the top earners, smaller fluctuations in income result in larger relative mobility. If the top quintile represents 50% of total income, one’s income has to change more in real-dollar terms in order to move two or more quintiles than if the top quintile represents 80% of total income. The range of incomes that characterize each quintile shrinks as income inequality between the top and bottom earners increases (that was part of what was happening in the 90s with the Dot Com bubble).

Income mobility doesn’t really provide much useful information, unless one buys Neo-Classical Economic Theory as a good general model of human economic behavior (it’s not*) and thinks that being able to move up or down in relative economic standing is a worthy goal in and of itself (as far as I can tell, that’s only true if one thinks large-scale income inequality is a good thing – if we all have near-equal income, for example, mobility is effectively meaningless, as a fluctuation of a thousand dollars might move one between the top and bottom quintiles).

*The simplifying assumptions NCE makes – the concept of ceteris paribus, or all things being equal – in order to be at all usable render it completely disconnected from actual human behavior and decision-making processes, as things are never, ever equal due to the influence of cultural and temporal context; NCE only works to describe sexless, genderless, raceless, nationality-less, shared-language, perfectly healthy, perfectly perfectly mobile (in terms of global mobility such that one can always move between localized markets if necessary – this is derisively and accurately known as “flat-Earth economics”, since it views the planet’s markets as without grades that inhibit mobility on the basis of various vectors of privilege), etc. and completely rational actors with access to complete and accurate information about every decision. The (unmarked/uninflected-by-any-aspect-of-privilege-or-marginalization) Rational Actor is an absurd fantasy, rendering pretty much all NCE, which relies on this model of human decision-making, a farce.

The idea that we live in a world where the simple, easy answers don’t necessarily work, and where just being a good-natured Forest Gump type isn’t going to guarantee you a great life doesn’t sit so well with these people.

As for science, science doesn’t allow anybody to be just a friendly dolt with a good heart – you have to *think* and it seems that conservatives hate thinking, since they believe so strongly that the old answers (platitudes) are always enough. The idea that we need new answers and new information and that we don’t already have the answers is deeply troubling to them, mostly because they believe all answers lie in tradition or ‘common sense.’ Science goes totally against that, and so they just dismiss science.