The auto insurance definition of accident frequency is essentially in basic terms how often an accident happens. There is generally a formula that is used by the actuaries of a carrier to figure out projected risk and in the end its a factor used in setting premiums. This statistical measure may take into account the accident rate climate in a particular state as well as a more narrow focus like how often young males are getting in crashes. The more frequently accidents occur the more people can expect to pay for their car insurance.
Another related variable is the rate of really destructive incidents which can also lead to more expensive coverage. This is especially true with the skyrocketing cost to treat people that may have been injured as well as the exhorbent costs to repair a vehicle.
If more conscientous consumers were aware of details like this they just might be more careful behind the wheel and in the end the save themselves and others some money on auto insurance premiums.