Over the past 20 years, skiing has become a relatively safe sport due to improvements in ski equipment  There has been a 50 percent drop in the number of ski injuries over the last 20 years
Clearly, however, there have not been decreases in the number of injuries in all categories, as statistical data readily show, for although broken legs and ankle injuries have decreased by an astounding 90 percent, knee injuries now represent 16 percent of all ski injuries, up significantly from the 11 percent of 20 years ago
It assumes that an increase in the proportion of knee injuries rules out a decrease in the number of knee injuries.