Not very well though, as we've seen; outlying data is a major problem with averages and that's why standard deviation exists.
To put it in context, Cork's crowds against Bohs, Bray (twice), Cobh, Pat's, Sligo and UCD (twice) were all higher than yours. They had the highest crowd in the three games involving yourselves, and the highest crowd in games against Drogheda. Derry only had higher crowds against Harps twice (the outlier which is distorting the average), Galway and Rovers. Add to that the fact that Cork's attendances are official and yours aren't and are probably overstated (as with most guesstimates), then your claim that Cork have "been getting 10% less than City all season" is simply wrong.