thanx for posting that link. But , I had to ask myself: isn't it a "given" that ... there will tend to be "higher end" jewelry and locations where people are "more affluent" ? Sure: go hunt beaches (or parks and schools) on the "good side of the tracks". Or where "the rich and famous play". Versus blighted bad side of town economically challenged zones
And would also note that the blighted/bad side of town parks/schools/beaches will be invariably riddled with more junk . Perhaps people are less "tidy" and more prone to drop their trash there, than at the upscale uppidity-up locations. Thus your ratios of aluminum to jewelry (aside from the caliber of said-jewelry) will be much worse at poor neighborhoods, vs affluent neighborhoods.