Sorry for OT - but to demonstrate my point...
It quite clearly shows the relationship between success and relative popularity, whilst showing the effect total population and infrastructure has as being of secondary importance.
Green = more Rugby clubs than Football clubs
Orange = more Football clubs than rugby clubs
Figures according to FIFA/IRB respectively.
Interesting, but its also a tad misleading in the case of New Zealand. For example Wellington's 'North Wellington' club, has probably nearly as many senior grade footballers, as just about every rugby club within Wellington. Where rugby clubs within rugby union have around six divisions of senior rugby (including social divisions) - there are 15 within Wellington alone.