Recent empirical investigations have shown enormous plant-level productivity heterogeneity, even within narrowly defined industries. Most of the theoretical explanations for this have focused on factors that influence the production process, such as idiosyncratic technology shocks or input price differences. I claim that characteristics of the output demand markets can also have predictable influences on the plant-level productivity distribution within an industry. Specifically, an industry’s degree of output market segmentation (i.e., the substitutability of one plant’s output for another’s in that industry) should impact the dispersion and central tendency of the industry’s plant-level productivity distribution. I test this notion empirically by seeing if measurable cross-sectional variation in market segmentation affects moments of industry’s plant-level productivity distribution moments. I find significant and robust evidence consistent with this notion.