The key factor in setting car insurance rates is the expense of paying for accidents and the costs associated with settling them. Other expenses relate to marketing the insurance (agent and broker salaries, commissions, expenses, and advertising), and general overhead (management and staff salaries and offices expenses).
But overall premium rates depends on other several factors like:
Past Claim records,
Catastrophe loss,
Underwriting experiences,
Volume of business,
Rates on which reinsurance cover is available,
Solvency Margin,
Administrative cost,
Mortality rates and many more to go.
