Wealth and poverty in historical samples

Since the lightning outside seems loath to end (great for atmosphere, lousy for electronics), I will be brief and to the point with this post.  Simple premise; how do we measure relative wealth and poverty in historical populations?  Two applications that I have used both at work and in my own research come to mind.  The first is this engine for converting historical currencies into present-day value (apparently, the $20 on my desk was worth $414.63 in 1700).  Second, the University of Virginia Library has an online Historical Census Browser that includes census data down to the county level since 1790 (although it does not enable finer, census tract analysis).  I have used this particular application for assessing the relative wealth of farmsteads at the county level using the agricultural schedule function.  It is also quite useful for assessing the ethnic composition of historical populations.