KEY POINTS:
The widely held belief that politicians can't keep promises has been turned on its head, but it appears telling the truth doesn't guarantee votes.
As the country enters an election campaign, a university study has found political parties have actually followed through on their pre-election promises at least half of the time. The same study found that voters do not tend to reward politicians who keep their promises by sticking by them.
Canterbury University political science student Nathan McCluskey found that, over the period 1972 to 2005, the rate of promises kept was as high as 90 per cent, but dropped to an average of 62 per cent under the Mixed Member Proportional (MMP) system.
He hit on the subject for his PhD after asking his father about what area of politics people would be most interested in.
"He said to me 'why don't you look at why politicians are such bloody liars?' And I thought that's a really good idea. We all talk about that."
He broke the pre-election pledges into "soft" and "hard" categories. The hard were easy to prove fulfilled or not, the soft relied more on a variety of statistics and commentary and his own judgment.
Mr McCluskey was "pleasantly surprised" to see the positive results were as high as they were. But he was most surprised to see a trend for parties delivering on more promises over time to have diminishing support from voters.
"The better they seem to do, the worse the support seems to get."
Former politician Richard Prebble said while all parties should be held to account over promises made, it was not as simple as keeping them or not. Promises made in opposition could prove to be mistakes when in power, damaging to the country or incompatible with other promises made.
"The real lesson is that political parties should promise less, and promise things more realistic, and be held accountable to it."
Former Alliance party leader Laila Harre said while the 1980s and 1990s were an "all-time low" for broken promises, in recent years Labour had succeeded by "under-promising" to voters.
Mr McCluskey hopes his research can help guide voters' decision-making.
"I would hope it does change perceptions and, more than that, there's some way for the information to be exposed before general elections, and so people have something to work off."
POLITICIANS AND PROMISES
The study found:
* The Labour and National Parties averaged about 80 per cent in keeping pre-election promises between 1972 and 1984.
* Between 1984 and 1996 the level dropped to an average of 69 per cent.
* It fell again to an average of 62 per cent following the introduction of the Mixed Member Proportional (MMP) system.
* Labour bucked the trend in its 2002-2005 term, delivering on 82 per cent of its key pre-election policies.
