Why do some countries use PR while others don’t? How electoral system trends spread across European democracies

Why do countries pick one electoral system over another? As Damien Bol , Jean-Benoit Pilet and Pedro Riera write, there is often an assumption that the choice of an electoral system is closely related to the calculations of dominant political parties who select systems that are likely to benefit them in elections. However based on a study of European countries between 1945 and 2011, they illustrate that the choice of an electoral system can be shaped significantly by the choices of neighbouring/similar states.