The stats I used in "Manchester A Football History" were the same stats that researcher Dr. Adam Brown used to ask the question: "Do You Come From Manchester". His research showed that Manchester had more Utd season ticket holders in it than City however my use of the same stats focused on each borough of Greater Manchester (excluding Wigan, Bolton and areas Adam had already discounted such as Mossley, Bramhall & Cheadle Hulme - areas I would have liked to include). I calculated how many season ticket holders each club had in each postcode borough and then painted my map based on whether it was Blue (more City s/t holders than Utd) or Red.
This proved that the region was more or less split with most of the West being Red (except M31 - blue!) and most of the East being Blue (except OL9).
Adam used the 'M' postcode as his definition of Manchester and so his conclusion that Manchester was Red was based on the fact that 6,678 City season ticket holders lived in M postcodes while 7,808 Utd s/ts lived in M postcodes. The problem with all of this is that 'M' does not mean Manchester. Denton is in Tameside not the city of Manchester; Old Trafford has a M postcode but not in the city of Manchester etc.
If only the City of Manchester postcodes are used than Manchester is Blue, but I chose to look across the Manchester region and include all the boroughs of Manchester (Salford, Trafford, Stockport, Tameside, Oldham plus Manchester) that the M60 cuts through or surrounds.
There are a few points that have to be explained with any research and my simple 'whose got most season ticket holders in a postcode borough' approach means that areas like Sale (M33) are perceived as Red because they have more Utd s/ts than City but it is also our 3rd highest concentration of S/ts in the region (it's Utd's number 1).
Statistics can be used in lots of ways, but if you want to see the breakdown of s/ts in each borough borrow "Manchester A Football History" (pages 489 to 498) from the library.
Cheers,
Gary