Of course it's from the uk, that's what I said, the chart said and what he was talking about too. An interesting factoid from the bbc article was that fully one third of all street seizures were less than 9% purity. That's really the worse in my mind than even the as low as 5% or 20% avg. numbers are. (<---- UK numbers!)
I can't find a nice chart like that for the US, but I found some numbers from 2007 from the DEA giving STRIDE and NFLIS seizure test numbers. All averages included both wholesale (10oz-kg++) and retail so they'll be much higher than actual coke people buy. STRIDE showed purity dropping from 67% in jan07 to 59% in jun07, and NFLIS had 56% in the winter and 53% in the summer.
They don't have purity only on a retail basis, but they do quote the average cost for a gram of pure (ie cost/purity). Since I can't talk price here I have to dance around it, but using their numbers and knowing pretty common prices for repress on the west coast I come up with single gram purities of about 35%-40%. I almost want to say that seems high in my limited experience. I used an even more common price for an 8 ball at first to figure it, but it came out so low at 20% I figured I'd do it with grams.
http://www.justice.gov/dea/concern/cocaine_prices_purity.html