I've updated the pollster house effects chart for EKOS in Canada and Quebec, incorporating the polling from the month of April 2010.
Nationally, the most favourable pollster for the Conservatives remains Ipsos-Reid, who has results for them 3.5 points higher than the average of the other pollsters. Their worst pollster is Harris-Decima, 2.4 points lower than the average.
For the Liberals, their best is Environics (+3.2) while their worst is Angus-Reid (-2.1).
The New Democrats' best pollster is Angus-Reid (+1.7) and their worst are Ipsos-Reid and Environics (-2.2).
The Greens' best pollster is Strategic Counsel (+2.3) while their worst is Angus-Reid (-2.2).
Speaking of Strategic Counsel, does anyone know if they have shut down for good?
In Quebec, the Bloc's best pollster is Harris-Decima (+2.8) while their worst is CROP (-3.7).
For EKOS, the pollster I've updated this month, they are the 6th best pollster for the Tories out of eight, the 4th best for the Liberals, 6th for the NDP, and the 3rd for the Greens.
In Quebec, they are the 4th best for the Tories (out of nine), worst for the Liberals, 4th best for the NDP, 5th best for the Bloc, and 2nd best for the Greens.
Just for fun, and as EKOS was the last poll released, let's tweak the national and Quebec numbers according to these latest findings:
Conservatives - 35.8%
Liberals - 24.2%
New Democrats - 16.4%
Bloc Québécois - 10.6%
Greens - 10.5%
This pushes the Conservatives up to potential majority territory due to the very low Liberal result.
Bloc Québécois - 41.7%
Liberals - 22.5%
Conservatives - 14.5%
New Democrats - 12.3%
Greens - 7.3%
This doesn't change the situation much in Quebec. The Bloc still has a dominant lead but the Conservatives are looking very weak and the Greens a little more realistic.
The chart below tracks how each pollster tends to lean when calculating support levels for the various parties, as compared to the average polling results from other pollsters each month. This does not necessarily equate to a deliberate bias, but instead is more reflective of the polling methods used - the "house effects". This is also not a scientific calculation of any kind, but it does give an indication of how each pollster tends to compare to others.
The following chart shows each pollster's average variation from other polling firms. The numbers are the amount of percentage points a particular pollster favours or disfavours that particular party compared to other pollsters over a similar period of time.