Statistical probabilities

The last three changes in government were not obviously foretold by publicly available polling data

Pollsters continue to debate the meaning and prominence of their work.

Gregg said the proliferation of sometimes conflicting polls and the hypeventilating analysis that frequently accompanies them does not strengthen democracy. On the contrary, he said: “Rather than have a public that’s informed, you have a public that’s misinformed.” He said he’s not arguing that polls should be ignored; only that their import needs to be interpreted much more cautiously. Rather than pontificate on weekly fluctuations in individual polls, he said it makes more sense to average the results of various surveys and look at the trends over longer periods of time.

It is probably important to consider, as Eric Grenier did this week, how much and how often polling responses change when an election campaign is conducted. Consider, for instance, that the last three changes in government were not obviously foretold by publicly available polling data released immediately before the election was called.

In November 2005, with a few exceptions, the lead for the governing Liberals was variously reported to be between five and nine points. An election was called on November 28 and two months later the Conservatives won the popular vote by six points.

A Gallup poll in August 1993, gave the Liberals a one-point lead over the governing Progressive Conservatives among decided voters, 34% to 33%. As to who would make the best prime minister, Kim Campbell led Jean Chretien by a wide margin, 47% to 24%. An election was called on September 8 and six weeks later Chretien’s Liberals won 41% of the popular vote and 177 seats in the House. Campbell’s Tories, with 16% of the vote, were reduced to two seats.

In June 1984, Gallup gave the governing Liberals a 12-point lead over the Progressive Conservatives, 40% to 28%. The new leader of the Liberal party, John Turner, enjoyed a 20-point lead over Brian Mulroney, 46% to 26%. An election was called on July 4 and two months later Mulroney’s Conservatives won 211 seats with 50% of the popular vote. Turner’s Liberals were reduced to 40 seats with 28% of the popular vote.

(All Gallup data via Carleton’s online library.)