I found figure 4.02 with age and gender data in bar graph form interesting. There's a rapid increase in accident rate for young riders, then a decrease for a while probably reflecting increasing rider skill, then an increase again in the 40s possibly reflecting complacency during routine riding, more aggressive riding associated with increased skill and perhaps a slight reduction in reflexes. The decrease approaching and following 50 is probably a combination of maturity, acknowledgment of slowed reflexes and perhaps fewer riders.
It was interesting that the male/female graphs showed similar trends.
We saw similar accident statistics for aircraft accidents while I was flying in the Navy. A peak due to inexperience followed by a decreasing rate and then an increasing rate that was most often attributed to overconfidence and complacency.
Ride within your limits, stay alert and wear protection.