Epidemiological Measures

While the quote below seems political but I actually want to use it to make an epidemiological point rather than discussing politics:

The most important intellectual pathology to afflict conservatism during the Obama era is its embrace of Ayn Rand’s moral philosophy of capitalism. Rand considered the free market a perfect arbiter of a person’s worth; their market earnings reflect their contribution to society, and their right to keep those earnings was absolute. Politics, as she saw it, was essentially a struggle of the market’s virtuous winners to protect their wealth from confiscation by the hordes of inferiors who could outnumber them.
 

One issue that I see over and over again is mistaking the measure for the outcome.  So people will fixate on body mass index as a measure of adiposity.  But doing so classifies Brad Pitt (famous for his muscles) as being either overweight or obese.  It is tempting to use an easy to measure correlated variable in place of the actual measure. 

For two people in the same position, there is a correlation between earnings and work (notice that I did not say a strong correlation).  It is tempting to assume, based on this micro-ordering, that the macro ordering of income is also related to the amount of work done or value created.  But it's obvious that this measure fails or else we would praise unions for working harder than regular workers rather than worrying that they were over-paid. 

I think that this problem is a consequence of us (as a society) wanting to assume clean values to soft and complex constructs.  We will all be better off if we resist this impulse.