It shouldn't be a surprise that auto insurance companies look at multiple characteristics when setting your insurance rates. A lot of this is automated now; you don't usually have an actual person pouring over your records. (This is why your premiums aren't negotiable.) Instead, the different categories that you fit into can be tallied up by a computer program to produce your premium cost. Different states have regulations about what can be taken into consideration, such as credit score, but there are a few things that every state lets insurance companies consider. The first is (obviously) your driving record. However, there are more.
Location by ZIP Code
If you live in a ZIP code where the car theft or burglary rate is high, or where there are known roads that are especially dangerous, your rates will be higher than those of someone living in a much less active ZIP code. The higher the risk that your car will be in an accident or have something happen to it, the higher your premiums will be. The rates associated with your ZIP code can change; neighborhoods do get safer or more dangerous over time, and insurance companies do keep an eye on those stats.
Age and How That Age Typically Drives
You'll find careful and careless drivers in any age range, but some age ranges are more prone to bad driving. Insurance companies look at accident and ticket statistics and determine which age ranges may be more of a risk to insure. These drivers may have to pay higher premiums until they reach the next age bracket. It may seem unfair, but risks do increase and decrease in general between ages.
What You Drive
When you drive a vehicle with a proven safety record and a body that does not compress easily, that can affect your rates. When you drive a vehicle with a proven record regarding longevity and ease of repair, that can affect your rates. Drivers who have vehicles where insurance may not have to pay out much will see lower premiums. However, keep in mind that some of the vehicles that people see as safe to drive are not that safe to people around them, such as very tall SUVs where you can't see pedestrians in front of your vehicle that well. That could make your premiums higher.
How Much You Drive
The more you're on the road, the more you increase your chances of being in a bad situation. That's a pretty basic issue for drivers; the more you drive, the more the odds are in favor of being in an accident, getting a ticket, and so on. If you can reduce your driving, you could reduce your premiums.
If your premiums are very high, call your insurance agent. There are a number of ways to either lower the premiums or break them up so that they are a little easier to pay.