I've updated the pollster house effects chart for Angus-Reid in Canada and Quebec, incorporating the polling from the month of July 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 (-1.9).
The New Democrats' best pollster is Angus-Reid (+1.9) 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 (-2.3).
In Quebec, the Bloc's best pollster is Harris-Decima (+2.8) while their worst is CROP (-3.7).
For Angus-Reid, the pollster I've updated this month, they are the 2nd best pollster for the Tories out of eight, the worst for the Liberals, the best for the NDP, and the worst for the Greens.
In Quebec, they are the 5th best for the Tories (out of nine), 8th best for the Liberals, 4th best for the NDP, 2nd best for the Bloc, and 7th best for the Greens.
Just for fun, let's tweak Angus-Reid's last national and Quebec numbers according to these latest findings:
Conservatives - 31.5%
Liberals - 30.9%
New Democrats - 17.1%
Greens - 11.3%
Bloc Québécois - 10%
Bloc Québécois - 35.3%
Liberals - 21.2%
New Democrats - 18.5%
Conservatives - 16%
Greens - 9.1%
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.