This came up in comments so, yes, whenever
mentioning the poverty rate, it's worth addressing the fact that though there's tons of disagreement as to how we
should measure poverty, pretty much everyone agrees that we
shouldn't be using the official poverty rate which is based on some outdated (and possibly never accurate) notions about the composition of household spending. Nevertheless, as is argued at the end of this
EPI snapshot there's no particular reason to think these problems detract from its value as an indicator of
trends.
This article available online at:
http://www.theatlantic.com/politics/archive/2007/08/trust-the-trend/46026/