Why do uninformed consumers pay more? A long-standing answer is market unfamiliarity. Yet how much it contributes to information frictions, and whether it fades with experience, have not been directly measured. I answer these questions using millions of fuel purchases by Japanese drivers. Identification exploits two kinds of variation in familiarity, from travel and relocation. Comparing the same driver across markets, I find that unfamiliarity accounts for 62% of the price gap between informed and uninformed consumers, while persistent individual differences explain the rest. This unfamiliarity-driven gap (the experience premium) declines with repeated purchases, consistent with learning in consumer search.
We study the impact of cartels on productivity using a novel plant-level dataset from the Japanese ready-mixed concrete industry, where cartels are legally permitted. After estimating plant-level productivity, we adopt a difference-in-differences design to show that cartel collapse increases plant-level and market-level productivity, while cartel formation has no effect. Furthermore, a triple-difference analysis reveals that productivity gains are more pronounced for initially less productive plants and those in high-density markets. These results, combined with decomposition analyses showing that market-level improvements are driven by within-plant changes rather than reallocation or exit, suggest that the treatment effect of competition drives productivity gains.