The process by which an innovation is communicated through certain channels over time, it describes a trend of sequential adoption of a policy or programme in different jurisdictions.
(Berry & Berry, cited in Stone 2004, 546 – 547)-----------------------------------
Policy diffusion is described as the spreading, dispersion or dissemination of ideas or practices from a common source. Rather than their conscious adoption, policies or ideas percolate into acceptance in other locales. Knill describes diffusion as the “socially mediated spread of policies across and within political systems, including communication and influence processes which operate both on and within populations of adopters.” (Knill 2005, 766) Diffusion can occur as a result of a number of different factors, in a range of contexts. Between states, a hegemonic power can have undue influence in precipitating the development of compatible policies in other nations. States can also be influenced by the actions of neighbouring states, or follow the lead of a pioneering state that develops what is recognized as an innovative policy. Policies can also diffuse upwards or downwards between national and sub-state governments. According to Stone, studies of diffusion tend to focus on the process and conditions for transfer rather than the nature and similarities of policies that are supposedly diffused. (Stone 2004, 546-7)
Knill, Christopher. 2005. “Introduction: Cross-National Policy Convergence: Concepts, Approaches and Explanatory Factors.” Journal of European Public Policy 12 (5): 764-774.
Stone, Diane. 2004. "Transfer Agents and Global Networks in the 'Transnationalization' of Policy." Journal of European Public Policy 11 (3): 545-566.