I have read a couple of pieces in the past 24 hours about the effect of demographic changes in the US on the employment-to-population ratio. As more retirees leave the labour force, this ratio will have a tendency to decline, although at present it is lower than the demographic change would seem to suggest. I like population aging as a macro theme, because it is based on analysis rather than starry-eyed storytelling; but I am not aware of a clean way to play it. Does anyone have any ideas?