There are really too many factors to consider to be comparing drivers like this. The factors include, but aren't limited to, policy limits, number of other insured vehicles, claim history, credit history, age, marital status, driving record, type of insurance, where you live, number of miles driven in the vehicle, ratio of insured vehicles to eligible drivers in the household, other policies held with the same insurer, history with that insurer, etc.
If you feel that you might not be getting a good deal, shop around your specific situation with various insurers, and compare apples to apples. Be sure that they're quoting you the exact same coverage (e.g., same limits, same type of coverage, same deductible in the case of comprehensive and collision, and same UM/UIM selection). You can always ask your current carrier to beat a quote from another company. Note--the "cut rate" companies often aren't. They either simply call themselves that, or only write policies for minimum limits (don't get me started on that--adequately insure yourself), or do things like quote you without UM/UIM coverage (again, don't fall for it).