Adding a teen driver to your household auto insurance policy can greatly increase your premiums no matter where you live.
However, some states are significantly more expensive than others.
Unfortunately, teens are "the riskiest drivers on the road" and insurance companies charge accordingly, says Carole Walker, executive director of the Rocky Mountain Insurance Information Association.
For the second year, a Quadrant Information Services study, commissioned by insuranceQuotes.com, examined the cost of adding a driver aged 16 to 19 to a family's car insurance policy in July 2014.
The study found that American families who add a teen driver to their existing auto policy have an average yearly premium increase of 79 percent, down from an increase of 84 percent a year earlier.
While experts aren't sure why the percentage dropped, a 2012 study by the University of Michigan found that fewer teens are driving than in previous decades.
Karl Newman, president of the Seattle-based NW Insurance Council trade group, says the growing use of graduated driver's license programs -- which delays licensing for teens -- has been a factor in reducing the cost of adding teen drivers to family insurance policies.
Newman says, "Adding a teen will continue to be a significant cost for families. However, it’s encouraging to see the decline."
According to a 2013 study by the AAA Foundation for Traffic Safety, fewer than half of teens get their license within 12 months of the minimum age for licensing in their state. About half were licensed before their 18th birthday.
Two decades earlier, over two-thirds of teens had their licenses when they turned 18.
Here are the seven most expensive states for adding teens to family auto policies and tips for keeping your teen safe.
The 2012 average insurance premium data is from the National Association of Insurance Commissioners (NAIC).
Average cost of car insurance: $741.51
Premium increase after adding a teen: 100.72%
Walker says one way to increase teen driver safety is to ride with teens from the time they've received a driver's license until you're convinced they're ready to drive alone. Having you in the car will train them to make good driving decisions.
"It's important for you to have supervised driving time with them," Walker says.
Average cost of car insurance (NAIC): $ 731.22
Premium increase after adding a teen: 101.42%
Kevin Foley, a New Jersey insurance agent, says you need to talk with your teen about the importance of defensive driving.
Make sure your teen knows that in addition to driving well, he or she must watch out for the other drivers’ mistakes, such as a driver not obeying a stop sign. It's important to explain to your teen that having the right of way doesn't mean other driver always will yield to him.
"Teens have no experience to draw upon, so you have to constantly remind them," Foley says.
Average cost of car insurance: $986.73
Premium increase after adding a teen: 102.40%
Encourage your teen to get good grades. Walker says most carriers grant discounts to students who maintain a grade-point average of 3.0 or higher. This is because insurers have found that good students typically file fewer car insurance claims.
Average cost of car insurance: $618.81
Premium increase after adding a teen: 105.55%
Mary Bonelli, a spokeswoman for the Ohio Insurance Institute, says one way to keep teens safe is to use electronic devices that monitor driving behavior.
Parents can monitor their teens' driving using small GPS-enabled devices that can be plugged into diagnostic ports located on automobile dashboards.
These devices check on such things as driving speed, vehicle location, acceleration and how hard teen drivers are braking. Typically, parents can go online to view their teen's driving route and statistics.
Such devices can alert parents of unsafe driving by text, phone or email, Bonelli says.
There also are a variety of mobile apps that help parents monitor teen drivers. For example, the Speedbump app for Android devices alerts parents when a teen's smartphone detects that the car they are riding in exceeds a predetermined speed.
Average cost of car insurance: $582.43
Premium increase after adding a teen: 106.93%
Newman says one of the best ways to keep teens safe is to make sure they drive safe cars.
Larger cars, such as full-size sedans and SUVs, typically provide better protection than compact models. You can review the Insurance Institute for Highway Safety's auto safety test results online at IIHS.org.
2. Rhode Island
Average cost of car insurance: $ 1,034.50
Premium increase after adding a teen: 107.35%
Foley says you can help your teens become safer drivers by setting a good example. If you have bad driving habits, such as talking or texting on mobile devices when you should be paying attention to the road, your teen may copy you.
1. New Hampshire
Average cost of car insurance: $716.84
Premium increase after adding a teen: 111.12%
Newman says teens should be reminded about the dangers of driving under the influence of drugs and alcohol. Make sure they don't think they can be intoxicated and drive safely.
"Not only can they be killed; they can end up killing others as well," Newman says. "It's a harsh topic, but we encourage people to address it."