No, you can’t predict the outcome of Canada’s 42nd federal election Benjamin Gregory Carlisle

The ability to forecast future events and plan for the future is a uniquely human skill, and a difficult one to master. Through a reframing of one’s memory known as Hindsight Bias, an event that was actually very surprising a priori may be perceived to have been predictable by a posteriori. Hence, I have attempted to quantify explicitly a sample of lay-forecasts of seat counts for the major political parties in the 42nd Canadian federal election.

Methods

Subjective probability distributions were collected using an online collection tool originally developed by Carlisle et al for the STREAM forecasting project. Predictors were shown a 20x20 grid, and allowed 40 “chips,” each representing 2.5% certainty, and instructed to place them in bins corresponding to ranges of seats that they predict will be won by each of the major five political parties. For example, if a forecaster placed 10 “chips” in the column labelled “0–16,” that would represent a forecast with 25% certainty that the party in question would receive between 0 and 16 seats in the House of Commons.

The forecast collection tool was available starting 10 days prior to the election, and was closed to new predictions at the time the first polls closed to voting. Forecasters were encouraged to make use of any external polls, articles or predictive models to which they had access, as this was meant to be a test of a person’s ability to produce a well-calibrated forecast of the election, not a test of the person’s memory.

Exclusions Forecasts were excluded if they appeared to not represent a good-faith attempt to provide a forecast, or if there appeared to be a fundamental misunderstanding of the forecasting task. Examples of excluded forecasts include: All cells left blank

All cells filled in

Alternating filled in and blank columns In the case of predictions where less than 40 chips were used, the used chips were re-weighted such that the sum of the probabilities of the used chips always equals 1. Forecasts of the Green Party and the Bloc Quebecois were not included in this analysis. These predictions were excluded because a grid of 20 ranges of approximately 17 seats per column does not allow for a sufficiently granular prediction space. Many forecasters placed 20 chips in the first column (the maximum allowed in a single column) and left the second column blank, while others filled the first two columns with 20 chips each, to use the allotted 40 chips. It was impossible to discern between those who would have used only the first column, had the option been explicitly given, and those who honestly meant to give a prediction that is twice as wide, and so these were excluded for simplicity.