This study investigates whether market experience eliminates the endowment effect, a phenomenon where individuals tend to value items more highly after owning them. The research examines trading behavior in two well-functioning markets: sports memorabilia at a sportscard show and collector pins at Walt Disney World's Epcot Center. The study uses both field experiments and auction data to test the hypothesis that market experience reduces the endowment effect. Key findings include: 1. **Endowment Effect**: Both markets show a significant endowment effect, where individuals are more likely to keep items they are initially endowed with. 2. **Market Experience**: As market experience increases, the endowment effect decreases. This is evident in both dealer and non-dealer groups, with dealers showing a stronger reduction. 3. **Institutional Robustness**: The results are robust to institutional changes and extend beyond the two markets studied. 4. **Selection vs. Treatment Effects**: The study controls for selection effects by examining trading rates of the same subjects one year later, finding that market experience significantly attenuates the endowment effect. The study concludes that market experience plays a crucial role in eliminating the endowment effect, providing strong evidence that neoclassical economic predictions are more closely approached as individuals gain market experience.This study investigates whether market experience eliminates the endowment effect, a phenomenon where individuals tend to value items more highly after owning them. The research examines trading behavior in two well-functioning markets: sports memorabilia at a sportscard show and collector pins at Walt Disney World's Epcot Center. The study uses both field experiments and auction data to test the hypothesis that market experience reduces the endowment effect. Key findings include: 1. **Endowment Effect**: Both markets show a significant endowment effect, where individuals are more likely to keep items they are initially endowed with. 2. **Market Experience**: As market experience increases, the endowment effect decreases. This is evident in both dealer and non-dealer groups, with dealers showing a stronger reduction. 3. **Institutional Robustness**: The results are robust to institutional changes and extend beyond the two markets studied. 4. **Selection vs. Treatment Effects**: The study controls for selection effects by examining trading rates of the same subjects one year later, finding that market experience significantly attenuates the endowment effect. The study concludes that market experience plays a crucial role in eliminating the endowment effect, providing strong evidence that neoclassical economic predictions are more closely approached as individuals gain market experience.