Ever heard of the Great Gatsby curve?  Nor had I (or should that be, I hadn't)  until I went to a seminar yesterday, and was told that it has             been getting the attention of some important people, including the White House - though whether that includes the actual Person in the White House is not sure. Anyway, the GGC shows a relationship between growing inequality on the one hand and diminishing social mobility (SM) on the other.  This makes pretty good intuitive sense, and also appeals to me politically, ie it's another black mark against increasing inequality.  But the presenter at the…