From the perspective of group affiliation of elected Legislative Assembly deputies (2009 and 2013), this paper adopts the number of valid returns in various geographical areas in order to calculate the Standardised Incidence Ratio (SIR) for individual candidate groups. It is aimed to investigate the difference in regional distribution of votes gained by groups with distinct affiliation, so as to manifest the possible relationship between the socio-economic backgrounds of voters and candidate group affiliation. The paper finds that in the circumstance of little divergence among political platforms of the competing groups, it is less likely that group affiliation casts very strong effect on voting behaviour.