The dataviz is nice, but I don't really see how this is useful to anybody, except maybe the Wikidata community doing navel gazing. 

Statements aren't, generally speaking, used in other Wikimedia projects hardly (such as in most Wikipedia infoxboxes) and thus aren't really visible to most Wikimedia readers. It doesn't seem like there's much incentive to improve verifiability of statements in Wikidata when they're not useful to anybody except maybe Google's Knowledge Graph. :P

A much more useful visualization would be the proportion of statements and other data from Wikidata actually referenced in places visible to users. Wikidata is not a project that is useful by itself, even if it was 100% perfectly verified by references. It only becomes useful through visibility to information consumers. 
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