Department of "Huh?"

A substantial amount of chatter about Stephanie Aaronson, Bruce Fallick, Andrew Figura, Jonathan Pingle, and William Wascher (2006), "The Recent Decline in Labor Force Participation and its Implications for Potential Labor Supply," Brookings Papers on Economic Activity (forthcoming) http://www.brookings.edu/es/commentary/journals/bpea_macro/forum/200603bpea_aaronson.pdf...

They ask the question: Is the recent decline in labor force participation primarily the result of a reduction in the proportion of the population that wishes to work (a supply-side shift caused by demographic, preference, and other factors), or primarily the result of a reduction in the proportion of the population that thinks it is worthwhile to search for work (as a result of a demand-side shift--weak labor demand in a long recession and then a sluggish recovery)?

The natural way to answer this question, it seems to me, is to do what economists always do: look at both quantities and prices. If the fall in participation is a supply-side phenomenon, we should have moved up and to the left along a demand curve, and should see falling employment-to-population and participation rates coupled with rising real wage and salary incomes. If If the fall in participation is a demand-side phenomenon, we should have moved down and to the left along a supply curve, and should see falling employment-to-population and participation rates coupled with falling real wage and salary incomes.

Aaronson et al. appear to do everything except this let's-draw-the-supply-and-demand-diagram first step that I thought was instinctive in every economist.

Hence I am left saying, "Huh?"