关键词: 拍卖理论, 关键字拍卖, 均衡分析, 预算约束

Abstract: Advertiser's budget constraint is an important factor which affects the bidding strategy equilibrium in keyword auctions. This research analyzes the equilibrium of budgeted keyword auction with the widely used generalized second price mechanism. The advertisers are divided into three types “born full winner” “born partial winner” “born loser” in accordance with the distribution of their click values and budgets, and the concepts “critical bids” and “key bids” are developed. Based on the repeated characteristic of keyword auctions the static model and dynamic model are developed respectively from the long-term view and short-term view. Studies have shown that there is unique pure strategy Nash equilibrium in the static environment and the auction converges to unique Nash equilibrium point in the dynamic environment when the advertisers adopt the best-response strategy, and in the dynamic environment the auctioneer's revenue is higher than that in the static environment. The numerical examples show that in the dynamic environment the auction converges to deferent equilibrium point with different initial bidding vectors. The results provide the auctioneer with a basis for decision making for the revenue forecast and auction mechanism optimization.

Key words: auction theory, keyword auction, equilibrium analysis, budget constraint