Risk 
Car insurance premiums are calculated primarily based on the risk presented to the insurer by the driver. The more likely a driver is to file a claim and cost the insurer money, the more you may pay for car insurance.  

The reason teenagers are costly to insure is because they are likely to file a claim. Teenagers are seen as less responsible and experienced than other drivers. They are also statistically more likely to participate in dangerous driving habits such as speeding. While this may not be true for every teenager, it is a general rule of thumb that insurers go by when calculating car insurance rates. 

This is also why adding a teen driver to your car insurance policy can cause your premiums to jump. Although your own record may be clean, adding another driver can always influence the cost of your premiums—especially when it comes to adding a teen driver. 

When Do Auto Insurance Rates Go Down? 
Car insurance premiums may start going down around the age of 20, but you may not see a significant drop in your rates until the age of 25. Age is only one factor of your insurance rates, however. Other factors could still influence your rates to make them go up or down regardless of age, such as your driving record. 

Different accidents can remain on a driving record for varying lengths of time. If your teen driver gets in a single at fault accident, for example, this incident may last on their record for around three years depending on where you live. Other incidents such as a DUI could remain on their record for up to 10 years, however. This means that their premiums will be influenced as long as the accident is on their record and they will not see a related drop until the accident leaves their driving record. 

Be sure to ask your insurance agent about ways you can save money while insuring your teen driver. You may qualify for discounts such as Good Student discounts and Low Mileage discounts