Watch your favourite types of music duke it out in the ring of public taste. Google has made a brave attempt to quantify the relative popularity of various strands of music since 1950 using objective criteria/data. Witness the massive displacement of previously dominant jazz by pop, rock and others. Watch the slow relative decline of rock as music contines to diversify and fragment. This article has some doubts about the methodology, but even if the results are not 100 percent reliable, imagine how many other axes/areas of human endeavour might fruitfully be subjected to this kind of approach.