This is a common problem in policy making known as the Lucas Critique[1]. But I don't think that it justifies avoiding any change to the voting system [1] http

This is a common problem in policy making known as the Lucas Critique[1]. But I don't think that it justifies avoiding any change to the voting system [1] http://en.m.wikipedia.org/wiki/Lucas_critique http://en.m.wikipedia.org/wiki/Lucas_critique