Distribution of axial ratios, q = b/a, for 4800 S0s (left) and 13,500 spirals (right) from the APM southern survey. Note that random orientations of circular flat disks would have a flat distribution in q = b/a. Deviations at low b/a are due to the presence of a bulge (boosting the minor axis) and at the high end because many spiral disks are slightly oval, not circular. (B&M Fig 4.46)