> A footnote: All the productivity gains in retail came from new stores,
>
> But since all labor in the retail sector is, by definition, unproductive,
> how can there possibly be any "productivity" gains in retail?
>
If by unproductive you're talking about Marx's idea of unproductive labor, I'm not enough of a scholar of Marxology to say where retail workers would fit in his schema. Obviously, though, the US government's statistical accounts that these data come from don't use the notion of unproductive paid labor.
I have to say that I don't see why retail workers should be seen as socially unproductive. Under any social system, someone has to arrange for goods to be shipped from factories to places where they can be conveniently purchased (i.e. "stores"), display them on shelves, make potential consumers aware of what's available and for how much (assuming we haven't yet achieved the higher stafe of communism), etc.
That's what's being measured when the "output" of the retail sector is recorded.
Seth