There’s a number of datasets out there that collate information about electoral violence in countries around the world (e.g. this one).  While I’m not an expert on them, I presume that the U.S. in recent decades has been coded a 0 for “no significant instances of electoral violence.”  Here’s fervently hoping that by tomorrow night the 2016 U.S. elections will not be coded as a 1 by future researchers.