In 2007, an all-time low point for the incidence of meningococcal disease, the CDC estimated that there were 1, 000 cases and 130 deaths nationally, compared with 2, 800 cases and 300 fatalities a decade earlier.

FORBES: Immunizing Bureaucrats Against Complacency

Arrington is convinced that, over time, the use of XP training will help lower the incidence and severity of injury because it creates educated coaches, who in turn develop educated players, which leads to fewer injuries and improved quality of competition.

FORBES: Cam Newton Versus 750,000 Youth Football Players

We know already that there is an unusual incidence of death of cloned animals around the time of birth.

BBC: Head-to-head: Cloning

History has shown, however, that spikes in the incidence of meningococcal disease can occur over a short time period and without warning.

FORBES: Immunizing Bureaucrats Against Complacency

One of the better prospective studies done on vitamin D and heart disease followed subjects over time, measuring vitamin D levels and following them to see who developed a first incidence of heart attack.

FORBES: Vitamin D: Still More Questions Than Answers

And the incidence of drunk driving by pro athletes who can easily afford their own full-time drivers but often choose not to reflects both an appalling lack of personal responsibility and recognition of the past shortcomings of others who thought they were above it all.

FORBES: Josh Brent, Drunk Driving, and Lessons from Army/Navy in Responsibility & Brotherhood