Is Life Expectancy Falling for One Group of Americans?

A study has been making it way around the left leans blogs lately that makes a startling claim.  Here is a post by  Kevin Drum at Mother Jones on the study.

Americans. Harold Meyerson is agog: "Clearly, they missed the recent study in Health Affairs which found that the life expectancy of white working class men fell by three years from 1990 to 2008, and that of white working class women

It looks like disturbing data but there is a simple huge flaw.  It looks from the chart like life expectancy for some group of Americans is falling, but since the group shrunk rapidly over the period of the study it is not showing what the bloggers say it shows.  

It may come as a bit of shock to some that people at the bottom of society by any of the usual measures (education, wealth, income) have lower life expectancy than those at the top but social scientist have known this for a long time (and note that correlation is not causation). So since so many fewer people fail to graduate high school today those who still do not graduate are from a lower group than than in the past.  To clarify what he is actually saying is: Since the bottom 5% today are living less long than the bottom 25% lived 25 years ago life expectancy is not increasing for all groups.

Now I would bat that Kevin Drum knows all this but you can shock people with stuff like this and sells ads and changes people's political positions.  

BTW One reason that someone would not gradate high school today would be very poor health (social science is not easy).