During the campaign, President-elect Donald Trump claimed that the United States carries a disproportionate share of the defense burden for protecting allies. The issue of allied contributions to the common defense is not a new one, with charges of "free-riding" by European allies in NATO dating back at least to the 1970s. Indeed, U.S. aid to other countries more broadly is consistently the least popular budget item in surveys of the American public. Does the U.S. really bear an unfair share of the burden for protecting allies? The reality is whether one considers a glass half full or half empty, and there are multiple glasses.