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A product search on an e-commerce site can return zero hits for several reasons. One major reason is that a user's query may not be appropriately expressed for locating existing products. To enable successful product purchase, an ideal e-commerce site should automatically revise the user query to avoid zero hits. We investigate what kinds of query revision strategies turn a zero-hit query into a successful query, by analyzing data from a major Japanese e-commerce site. Our analysis shows that about 99% of zero-hit queries can be turned into successful queries that lead to product purchase by term dropping (27%), term replacement (29%), rephrasing (17%), and typo correction (26%). The results suggest that an automatic rewriter for avoiding zero-hit product queries may be able to achieve satisfactory coverage and accuracy by focusing on the above four revision strategies.

We investigate a firm's pre‐emptive behavior by comparing Cournot competition and Stackelberg games with one leader and multiple followers, where each firm has access to private information on stochastic demand. We show that the firm prefers pre‐emptive quantity choice (Stackelberg leader) to simultaneous quantity choice (Cournot firm) if and only if the firm is ignorant of the market size compared to the other firm. The firm's decision in terms of production timing is always detrimental to producer surplus in the industry. It is beneficial to consumer surplus in duopoly competition, but detrimental when there are many competitors in the market.

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