This empirical study of patent claim definiteness cases of the past decade makes several novel findings including: (1) slightly more than half of final Federal Circuit definiteness cases hold the asserted claims not indefinite; (2) the percentage of non-Federal Circuit definiteness cases holding claims not indefinite increased approximately 60 percentage points over the ten-year period focused on in this analysis;(3) the Federal Circuit more often held chemical claims not indefinite, but electrical claims indefinite; and (4) the Federal Circuit more often held claims with term clarity issues not indefinite, but claims with means-plus-function issues indefinite. These differences partially result from the Federal Circuit incorporating an evidentiary burden into the "insolubly ambiguous" standard and inconsistently applying the "insolubly ambiguous" standard. After describing other effects of this standard, this Article recommends that the Federal Circuit modify, clarify, or abolish the "insolubly ambiguous" standard.