David Farrar did two things this morning: first, he posted a carefully truncated graph that got people talking, showing what he claimed is evidence of Labour’s popular decline – with a trendline added in “to reinforce the obvious point” – and, second he didn’t post a similar graph showing the declining trend in support for National, his own party.
Lindsay Mitchell fixed the second omission. Below is her graph showing National’s long-term trend in support since 1938. She also added in a trendline “to reinforce the obvious point.” Like Labour’s, it too declines – in part due to MMP dividing up the vote between more parties than heretofore, and partly due to the slow rise of Helen Clark and the dramatic fall of Bill English in 2002:
So why did Farrar choose 1938 as a starting point rather than Labour’s actual starting point in 1919?
Perhaps because that 1938 election delivered an all-time high result for Labour, allowing the remaining results to show the dramatic decline he desired.
It’s a little bit of a statistician’s simple sleight-of-hand that most of the commentariat has bought almost without demur.
If however we were to do the job his selective starting point obscures, to start instead with the post-war 1919 election instead (the first election in which the modern Labour Party was a force) we’d see a somewhat different “trend.”
I’ll let you draw your own long-term trend line, or medium-term cycle lines, if you think any of them them appropriate.
And I”ll add a link to what must be one of David’s favourite books:
UPDATE: If there is a political party with a genuinely discernible trend, perhaps it is this one …
Answers for which on a postcard, please.