ABSTRACT
The Jenkins Commission has recommended an innovative AV Plus system as the alternative to plurality rule to be offered in an electoral systems referendum. Eighty-five per cent of MPs would be elected in local constituencies somewhat larger than at present, and the remainder in 80 top areas. We show how the Commission came to its finished scheme, and evaluate its likely effects using detailed simulations of the 1997 and 1992 general elections. We compare the systems’ implications in terms of deviation from proportionality and the better territorial representation of parties’ vote bases. AV Plus represents a considerable advance on plurality rule, but in 1997 conditions would secure only ‘broad’ proportionality, in particular performing worse than the straightforward AMS alternative using the same local:top up ratios and top up areas proposed by Lord Alexander. However, in 1992 conditions AV Plus performs reasonably proportionally, and almost as well as AMS.
