Evidence is growing that forms of incivility–e.g. aggressive and disrespectful behaviors, harassment, hate speech and outrageous claims–are spreading in the population of social networking sites’ (SNS) users. Online social networks such as Facebook allow users to regularly interact with known and unknown others, who can behave either politely or rudely. This leads individuals not only to learn and adopt successful strategies for using the site, but also to condition their own behavior on that of others. Using a mean field approach, we define anevolutionary game framework to analyse the dynamics of civil and uncivil ways of interaction in online social networks and their consequences for collective welfare. Agents can choose to interact with others–politely or rudely–in SNS, or to opt out from online social networks to protect themselves from incivility. We find that, when the initial share of the population of polite users reaches a critical level, civility becomes generalized if its payoff increases more than that of incivility with the spreading of politeness in online interactions. Otherwise, the spreading of self-protective behaviors to cope with online incivility can lead the economyto non-socially optimal stationary states. JEL Codes: C61, C73, D85, O33, Z13. PsycINFO Codes: 2240, 2750.

In this model, well-being depends on leisure, on an environmental renewable resource, and on a non-storable output, which can substitute for the environmental resource or can satisfy needs different from those satisfied by the resource. Individuals have free access to the environmental resource, which is subject to negative externalities: that is, is depleted by the production and consumption of the output. Individuals react to negative externalities by increasing their labour supply in order to produce substitutes for the diminishing resource. The increase in production and consumption that ensues generates further deterioration of the future quality or quantity of the free resource, thus giving rise to a self-reinforcing process. Multiple equilibria and ‘critical mass effects’ are consistent with the functioning of this economy and the resulting level of aggregate production may be higher than is socially desirable.

We set up a theoretical framework to analyse the role of economic growth and technological progress in the erosion of social capital. Under certain conditions on parameters, the relationship between technological progress and social capital can take the shape of an inverted U curve. Furthermore, we show the circumstances that allow the economy to follow trajectories where the stock of social capital grows endogenously and unboundedly.