Average-wage-by-major statistics have become widely available to students interested in the economic ramifications of their college major choice. However, earning a major with higher average wages does not necessarily lead individual students to higher-paying careers. This essay combines literature review with novel analysis of longitudinal student outcomes to discuss how students use average-wage-by-major statistics and document seven reasons that they may differ, sharply in some cases, from the causal wage effects of major choice. I focus on the ramifications of two-sided non-random selection into college majors, mismeasurement of longitudinal student outcomes, and failures of extrapolation between available statistics and student interests. While large differences in average wages by major are likely to indicate causal ordinal differences between fields, small differences are probably best ignored even by students with strong interest in the economic consequences of their major choices. This essay is adapted from Chapter 6 of "Metrics that Matter: Counting What's Really Important to College Students."