This Web Appendix provides background and more detail for the paper. It has five sections, the last of which, containing figures, is in a separate pdf file:A. Interaction between value adjustment and the bidding trade-off in first-price auctions.B. Calculation of First- and Second-Price Equilibrium, Cursed Equilibrium, and Level-k Bidding Strategies for Kagel and Levin's (1986), Avery and Kagel's (1997) and Goeree, Holt and Palfrey's (2002) Experimental Designs.C. Estimates for Level-k plus Equilibrium Models with versus without Truthful Types.D. Estimates of Subject-specific Precisions and Standard Errors (starts at A-29).E. Logit Bid Densities for Random L1, Random L2, Truthful L1, Truthful L2, and Equilibrium and Representative Precisions.(For section E see: "Supplementary material for "Level-k Auctions: Can a Non-Equilibrium Model of Strategic Thinking Explain the Winner's Curse and Overbidding in Private-Value Auctions?": Graphs").