We investigate a dynamic model of network marketing in a small-world network structure artificially constructed similarly to the Watts-Strogatz network model. Different from the traditional marketing, consumers can also play the role of the manufacturer's selling agents in network marketing, which is stimulated by the referral fee the manufacturer offers. As the wiring probability α is increased from zero to unity, the network changes from the one-dimensional regular directed network to the star network where all but one player are connected to one consumer. The price p of the product and the referral fee r are used as free parameters to maximize the profit of the manufacturer. It is observed that at α = 0 the maximized profit is constant independent of the network size N while at α = 0, it increases linearly with N . This is in parallel to the small-world transition. It is also revealed that while the optimal value of p stays at an almost constant level in a broad range of α, that of r is sensitive to a change in the network structure. The consumer surplus is also studied and discussed.

We examine the effect of competition on the incentive of firms to disclose quality to consumers before trade when information disclosure is not costless. We demonstrate that no firm will disclose information in the limit, no matter how small the disclosure cost is; that is, the market outcome converges to complete concealment of information as the number of competing firms becomes larger. Nonetheless, it can be shown that under a mild condition, the equilibrium amount of information disclosure is socially excessive for any number of firms, so discouraging information disclosure by levying a tax may increase social welfare.

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Infinitely repeated interaction between a defendant and a plaintiff can enhance the credibility of cheap talk and improve efficiency in outcome that would be infeasible without cheap talk. The basic driving force is reputation effect. If the players are concerned about their reputation, cheap talk cannot be taken as meaningless even in a game where the interests of the players are sufficiently conflicting, because possible current gains from opportunistic behavior can be wiped out by future losses in payoff from damaged reputation.

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