Demographics is arguably not a subject in a category but rather a tool or lens in which we can provide certain interpretations of virtually all the categories listed listed here. The science, the pitfalls of how you gather data, of what questions are to be asked to whom, and what it all means can be daunting. On the other hand any response on YELP or other feedback mechanisms are just a simpler form of a demographic. I suppose you can see demographics as just a way of trying to segregate a field of information into categories or trends of some sort.
I will say personally that I have had some correspondence with a famous Berkeley professor on the subject of what it takes for a grassroots group of local folks to run a scientifically valid poll on any given subject. He said it could be done by 20 to 30 people working a few days. The point being that we need not only wait for government agencies, or private business. to be run the show in terms of measuring the pulse of democracy on any series of issues. However even raising the idea of democracy often brings us the sense of a completion is at the basis of demographically and polling research, so perhaps even that is a poor choice of terms. It does reveal however how tricky both the starting point and the perceived end product is for the scope of the demographic research to be done
Also worth noting is demographics reports are not solely designated to the health status of community members but can also be used to gather information on attitudes about various health related issues