Environmental ministry onset. The variable is coded "1" on the year when a national environmental ministry got established. For the rest of the years, the variable is coded "0". The authors expanded temporal and spatial coverage of the data initially published in the article:

Busch, P.O. and Jörgens, H., 2005. The international sources of policy convergence: explaining the spread of environmental policy innovations. Journal of European public policy, 12(5), pp.860-884.