When and where has proportional representation been instituted?
The definition of 'proportional representation' is contested. Variants include Mixed-member, Partly-list, Single transferable vote, Cumulative voting and others. None of these are intended to extend to a random selection of citizens in order to select a representative sample of the population.
Given the limitations of the definition, the fact is that more than half of the world's countries use some form of 'proportional representation', usually connected to balloting through a political party.