Abstract: The recent decade has witnessed the development of internet technology and widespread use of electronic commerce. While the emerging electronic markets, such as Taobao and eBay, have achieved huge number of market transactions at a daily basis, efficient contract designs are still missing for the market owners to extract greater monetary benefits from the third-party sellers' sales in the market. Currently, the most popular form of contract is the commission contract based on the sales history of each seller, which implicitly assumes that sales history is positively correlated with future sales but overlooks the influences of other factors such as seasonal effects, fashion pattern, and potential substitutes, etc. In this paper, an innovative contract design for the owners of electronic market is provided by taking advantage of third-party sellers' private expectation on future sales. In the beginning of each period, upon observing the sales history, the owner offers a customized menu of contracts to the third-party seller. The seller reveals her private information by selection the contract designed for her type. The optimal contract design problem is solved and a simple decision rule is discovered for the contract design. The optimal contract parameter can be given by a function of the failure rate of the estimating distribution of the correlation coefficient. The superiority of this contract is verified by a set of computer simulation study. The numerical results verify that the market owner's profit can be improved by benefiting from the seller's private information. Given the convenience of implementation in the online channels, this type of contract is expected to help owners of electronic market quickly refine their contracting with third-party sellers.

Key words: electronic market, dynamic contract, information asymmetry