I couldn't even tell what it was measuring until seeing it explained in the Twitter comments. Apparently it's an estimate of the percentage of American adults w

I couldn't even tell what it was measuring until seeing it explained in the Twitter comments. Apparently it's an estimate of the percentage of American adults who think violent crime is a problem, for whatever reason going backwards through time at a non-uniform rate. Even after that being explained, I don't see anywhere this is indicated on the graphic, so I have to assume this person looked it up using Pew Foundation's real publication.