I've updated the pollster leanings chart for all of the national pollsters, except Strategic Counsel, incorporating the polling from the month of February 2010
Quebec has not been updated yet, but will be.
The top pollster for the Conservatives is Ipsos-Reid, which tends to poll them 3.5 points higher than other pollsters. The worst for the Conservatives is Harris-Decima, 2.4 points below average.
The top pollster for the Liberals is Environics, which tends to poll them 3.2 points higher. The worst for the Liberals is Angus-Reid, which polls them 2.1 points lower than the others.
For the NDP, the best pollster is Angus-Reid, 1.7 points higher than average. The worst are Ipsos-Reid and Environics, 2.2 points lower than average.
And for the Greens, the best pollster is the Strategic Counsel, 2.3 points higher than average. The worst is Angus-Reid, 2.2 points lower than average.
Léger Marketing and EKOS seem to be the pollsters with the fewest outliers. Léger Marketing doesn't have a variation of more than one point, while EKOS doesn't have one of more than 1.5 points.
Just for fun, let's take Angus-Reid's poll yesterday and apply these numbers to it:
Conservatives - 35% = 33.8%
Liberals - 29% = 31.1%
New Democrats - 20% = 18.3%
Greens - 7% = 9.2%
Bloc Québécois - 9% = 9%
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. 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.