H S Dent has a set of endlessly fascinating demand curves that show the demand for various kinds of consumer goods by the age of the consumer. Many of these are pretty much what you'd expect: demand for bicycles, for example, grows until about age 40 and then drops off to nothing a little after age 80. Still, there's a lot of surprises.
Children's clothing (of all sorts) drops off with increasing age as you'd expect but then rises again at a little after age 80. You see this again and again in everything from boys' underwear to girls uniforms. I have no idea why this is. Oddly, adult clothing doesn't follow the same pattern: you generally see the expected drop off with increasing age. Not all the curves show an increase to some age and then a decrease. Some rise and fall repeatedly throughout the age span—college tuition is an example of this. Some, like safe deposit box rental and prescription drugs shows a steady increase throughout the age span.
I doubt any of this is of particular importance to the typical Irreal reader but I find the graphs entertaining and in some cases puzzling. It well worth a look—you may be surprised at how interesting they can be.