This paper presents a theory of auctions and competitive bidding, analyzing different auction formats and their implications for pricing and bidder behavior. The authors develop a general auction model that incorporates both private and common value scenarios, as well as risk-neutral and risk-averse bidders. The study shows that the English auction typically generates higher average prices than the second-price auction, while the second-price auction outperforms the Dutch and first-price auctions when bidders are risk-neutral. The model also demonstrates that expert appraisals can increase expected prices in all auction formats. The paper discusses various auction forms, including the English, Dutch, first-price, and second-price auctions, and their implications for pricing and bidder behavior. It highlights the strategic equivalence between the Dutch and first-price auctions, and between the English and second-price auctions under certain conditions. The authors also explore the impact of risk aversion on auction outcomes, showing that risk-averse sellers prefer the Dutch or first-price auctions over the English or second-price auctions. The paper also examines the role of information in auction outcomes, showing that public information can increase expected revenues. It demonstrates that the expected price in the English auction is not less than that in the second-price auction, and that public information can raise revenues. The authors conclude that the English auction is generally more effective than the second-price auction in generating higher expected prices, and that the optimal auction format depends on the specific characteristics of the item being sold and the bidders' information. The paper provides a comprehensive analysis of auction theory, offering insights into the design and conduct of auction mechanisms.This paper presents a theory of auctions and competitive bidding, analyzing different auction formats and their implications for pricing and bidder behavior. The authors develop a general auction model that incorporates both private and common value scenarios, as well as risk-neutral and risk-averse bidders. The study shows that the English auction typically generates higher average prices than the second-price auction, while the second-price auction outperforms the Dutch and first-price auctions when bidders are risk-neutral. The model also demonstrates that expert appraisals can increase expected prices in all auction formats. The paper discusses various auction forms, including the English, Dutch, first-price, and second-price auctions, and their implications for pricing and bidder behavior. It highlights the strategic equivalence between the Dutch and first-price auctions, and between the English and second-price auctions under certain conditions. The authors also explore the impact of risk aversion on auction outcomes, showing that risk-averse sellers prefer the Dutch or first-price auctions over the English or second-price auctions. The paper also examines the role of information in auction outcomes, showing that public information can increase expected revenues. It demonstrates that the expected price in the English auction is not less than that in the second-price auction, and that public information can raise revenues. The authors conclude that the English auction is generally more effective than the second-price auction in generating higher expected prices, and that the optimal auction format depends on the specific characteristics of the item being sold and the bidders' information. The paper provides a comprehensive analysis of auction theory, offering insights into the design and conduct of auction mechanisms.