This paper studies the diffusion of products and behaviour with coordination effects through social networks when agents are myopic best responders. We develop a new network measure, the contagion threshold, that determines when a p-dominant action—an action that is a best response when adopted by at least proportion p of an agent’s opponents—spreads to the whole population starting from a group of players whose size is smaller than half and independent of the population size. We show that a p-dominant action spreads to the whole network whenever the contagion threshold of that network is greater or equal to p. We then show that in settings where agents regularly or occasionally experiment and choose non-optimal actions, there exists a threshold level of experimentation below which a p-dominant action is chosen with the highest probability in the long run. This result implies that targeted contagion, a network-wide diffusion of actions initiated by targeting agents, is justified even in settings where agents’ decisions are noisy.

本文研究了当代理人是近视最佳反应者时，具有协调效应的产品和行为通过社交网络的传播。我们开发了一种新的网络度量，即传染阈值，它确定何时p主导的行动——当至少有p代理的对手采用时是最佳反应的行动——从一组玩家开始传播到整个人群其规模小于一半且与人口规模无关。我们表明，每当该网络的传染阈值大于或等于p时，p主导动作就会传播到整个网络. 然后我们表明，在代理定期或偶尔进行实验并选择非最优动作的设置中，存在一个实验阈值水平，低于该阈值水平，从长远来看，以最高概率选择p主导动作。这一结果意味着，即使在代理决策嘈杂的环境中，目标传染，即由目标代理发起的行动在网络范围内的扩散也是合理的。