On the negative side, the Single Non Transferable Vote (SNTV), as a semi-PR system, is still not able to guarantee that the overall parliamentary results will be proportional. Small parties with say around ten percent support, whose votes are widely dispersed, may not win any seats, and larger parties can receive a substantial 'seat bonus' which propels a national plurality of the vote into an absolute parliamentary majority. In 1980, the Japanese Liberal Democrats won fifty-five percent of the seats with only forty-eight percent of the votes (see Japan - Electoral Reform).
The proportionality of the system can be increased by incrementally increasing the number of seats to be filled within multi-member districts, but this weakens the voter-MP relationship that is so prized by those who advocate defined geographical districts. Multi-member districts of nine members in Jordan, and seven members in Vanuatu, are at the very top end of manageable SNTV constituencies.
As SNTV gives voters only one vote, the system contains few incentives for political parties to appeal to a broad spectrum of voters in an accommodating manner. As long as they have a reasonable core vote, they can win seats without needing to appeal to 'outsiders'. Furthermore, the fact that multiple candidates of the same party are competing for the same votes means that internal party fragmentation and discord can be accentuated, and that 'clientelistic' politics, where politicians offer subtle electoral bribes to groups of defined voters, is exaggerated.
Finally, SNTV requires parties to consider complex strategic considerations of both nominations and vote management. Putting up too many candidates can be as unproductive as putting up too few, and the need for a party to discipline its voters into spreading their votes equally across all a party's candidates is paramount.
