Once policies are adopted, a key challenge is to make sure that all stakeholders comply with regulations or follow the recommendations. It is well known how the greatest resistance to a policy is not active opposition, but lack of application.

For instance, several programmes to reduce alcohol dependency problems in the UK failed as they excessively relied on positive and negative incentives such as prohibition and taxes, but did not take into account peer-pressure and social relationships. They failed to leverage “the power of networks” (Ormerod 2010). For instance, any policy related to reduction of alcohol consumption through prohibitions and taxes is designed to fail as long as it does not take into account social networks, as binge drinkers typically have friends who also have similar problems. In another classical example (Christakis and Fowler 1997), a large scale longitudinal study showed that the chances of a person becoming obese rose by 57 per cent if he or she had a friend who became obese.

The identification of social networks and the role of peer pressure in changing behaviour is not considered in traditional policy-making tools.