How Much Ammo Should I Carry--Another Data Point

In "Explaining The Need To Carry Spare Ammo," Massad Ayoob relates:

At about the same time on the very informative site pistol-forum.com, readers, heard from Dr. Gary K. Roberts, a protégé of the late wound-ballistics expert Dr. Martin Fackler. Since Fackler’s passing, Roberts is generally considered today’s leading expert on the topic. Dr. Roberts wrote, “Looked at in aggregate over a multi-year period, the data breaks down like this: Approximately 1/3 of the time only one shot was needed to stop the threat. In another 1/3 of cases, 2–9 shots were required. Unfortunately, 10+ shots were necessary to stop the criminal aggressor in the final 1/3 of violent encounters.”