How about this as a new indicator. Great songs in early to mid sixties. However, in the late sixties, pop songs were progessively becoming too heavy for the casual listener. Almost all seventies songs are completely boring (for those of us who were born after). The eighties saw a classy resurgence of bands and styles, so did the early to mid nineties. 80s materialism was there for a reason. Perhaps piercings/tatoos increase when the economy is about to make a downturn. Now I get so bored listening to new pop songs, which gives me the impression that the economy is to stay sluggish.