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This essay surveys the literature on directed search and competitive search equilibrium, covering theory and a variety of applications. These models share features with traditional search theory, but also differ in important ways. They share features with general equilibrium theory, but with explicit frictions. Equilibria are often efficient, mainly because markets price goods plus the time required to get them. The approach is tractable and arguably realistic. Results are presented for finite and continuum economies. Private information and sorting with heterogeneity are analyzed. While emphasizing issues and applications, we also provide several hard-to-find technical results. (JEL D50, D83)

Largely applied to internal threading of extruded tubes, cold form tapping is now becoming a promising process for internal threading of holes in non ferrous and ferrous solid components, more particularly for mass production in the automotive industry. The aim of this study is to present the surface properties of the threads resulting from form tapping. Geometrical characterization, surface texture, mechanical and metallurgical observations are investigated. The results obtained are discussed according to the input parameters of the process, and are compared to those obtained from cut tapping. The strength of the work material and the influence of the lubricant are the two main parameters affecting the process, and a correlation with the tapping torque is proposed. Finally, the characteristics of the thread surface depend on the parameters of the tapping operation, thus it has to be taken into account in the design approach when this tapping process is chosen.

This essay surveys the literature on directed/competitive search, covering theory and applications in, e.g., labor, housing and monetary economics. These models share features with traditional search theory, yet differ in important ways. They share features with general equilibrium theory, but with explicit frictions. Equilibria are typically efficient, in part because markets price goods plus the time required to get them. The approach is tractable and arguably realistic. Results are presented for finite and large economies. Private information and sorting with heterogeneity are analyzed. Some evidence is discussed. While emphasizing issues and applications, we also provide several hard-to-find technical results.

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We study the implementation of constrained-efficient allocations in labour markets where a basic coordination problem leads to an equilibrium matching friction. We argue that these allocations can be achieved in a non-cooperative equilibrium if wages are determined by ex post bidding. This holds true even in finite-sized markets where the equilibrium-matching process has decreasing returns to scale -where the 'Hosios rule' does not apply -both with and without heterogeneity. JEL classification: D83, J64Enche`re ex post et choˆmage efficient de coordination. Les auteurs e´tudient la mise en oeuvre d'allocations axe´es sur l'efficacite´dans des marche´s du travail ou`un proble`me fondamental de coordination engendre un e´quilibre frictionnel. On sugge`re qu'on peut atteindre ces allocations dans un e´quilibre sans coope´ration si les niveaux de salaires sont de´termine´s par des enche`res ex post. Cela demeure vrai meˆme dans des marche´s de taille finie ou`le processus d'e´quilibration fait l'expe´rience de rendements de´croissants a`l'e´chelle -la`ou`la re`gle d'Hosios ne s'applique pas -a`la fois quand il y a et qu'il n'y a pas d'he´te´roge´neite´.

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We compare equilibrium allocations in directed search models where prices are determined alternatively by posting and by competing auctions, with the following results. With finite numbers of players, sellers' expected payoffs are higher when all sellers auction than when all sellers post. This difference is largest in the 2-by-2 case, where payoffs to sellers are 1/3 higher if they auction. The difference in the payoffs decreases rapidly with market size and vanishes in the limit "large" economy. When sellers can choose whether to post prices or auction in the 2-by-2-case, all combinations (auction-auction, post-post, and auction-post) can occur in equilibrium if sellers choose mechanism and price simultaneously. However, if sellers choose mechanism before price then the dominant strategy equilibrium has both sellers auctioning.