Frustratingly, the post you are probably thinking of was here: http://www.cpeterson.org/2011/03/10/why-gas-is-so-expensive-today-hint-its-not-libya-2/ http://ww

Frustratingly, the post you are probably thinking of was here: http://www.cpeterson.org/2011/03/10/why-gas-is-so-expensive-today-hint-its-not-libya-2/ http://www.cpeterson.org/2011/03/10/why-gas-is-so-expensive-... (Aside: this is one reason why I have so little trust in the web as a long-term historical medium.) Although that article focused primarily on oil futures, it also discussed commodities futures, and specifically addressed the rollovers. Unfortunately, I neither understood it well enough at the time, nor remember it well enough now, to regurgitate it. Maybe someone else will come along with a cached copy.