Ok, so there's been a whole lotta graphs floating around on the blogosphere recently purporting to show how absolutely disastrous the trend has been for the left and how totally unprecedented and awful things are for Labour.
Given that we live in an MMP environment, I thought'd be interesting to see the trend for left vs. right overall, rather than looking solely at the major parties.
It's interesting comparing this to the other charts, and it paints a somewhat less depressing picture for the left*. The downward trend for the left pretty much begins in the 1980s, which I don't find particularly surprising. Also interesting to note the huge advantage of the left bloc from the 1950s through to the early 1990s, despite National's dominance in government over this time. Yay for MMP, basically!
*I've taken "left" to include Labour, Democrats/Social Credit, Values, Greens, NewLabour, Alliance, Progressive, and Mana/IM. "Right" includes National, NZ Party, ACT, and Conservative. "Centre" parties, which are left out of this graph for simplicity, but includes NZ First, United Future, and Māori. Parties which have failed to poll > 1% for at least two successive elections have been consigned to the "other" category, and also left out.