This is based upon the total scores of the top teams in each of the N and S hemispheres over the previous 3 years. Where a team includes members located in both N and S (e.g. ROC with Nigel in ZD7), the calculation is based upon participants of either team in N and S (e.g. in 2012 Nigel is moved across to the VK Team for the purposes of calculating the Factor)
An unequal number of team participants in N and S can therefore sometimes arise and so the Correction Factor is derived from the average rather than the total N and S scores.