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Insuring a vehicle costs more during winter

Joseph Murphy is the state insurance commissioner.

Joseph Murphy is the state insurance commissioner.

Here’s another reason to watch out for winter in Massachusetts: higher car insurance prices.

A new, yearlong study by an online insurance shopping firm found that drivers can spend as much as 20 percent more if they purchase policies in March instead of in the summer. Prices jump in January and February, too.

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“Most consumers just believe that the rate is the rate and it just sticks,” said Laura Adams, a senior analyst with Insurancequotes.com. “We were surprised by the amount of variability.”

In Massachusetts, the lowest prices were found from June to September. The average premium for a Massachusetts driver was $1,011 in 2011, according to the most recent data available from the National Association of Insurance Commissioners. So if consumers bought policies at the average cost in July, they could pay $200 more if they purchased them in March.

The cost swings in Massachusetts were the 15th largest nationwide, according to Insurancequotes.com. Hawaii ranked number one with a nearly 50 percent difference between the cheapest month for its state residents to purchase auto insurance, December, and the most expensive month, March.

Wyoming, the District of Columbia, Maryland, and Pennsylvania followed behind with high variations. South Dakota, Arkansas, and Utah had the most stable prices throughout the year.

The report looked at data from the top carriers in each state. Nationwide, the average difference between the cheapest and most expensive month was 7.5 percent.

Insurancequotes.com only looked at one year of data, so it is unclear if the monthly patterns are recurring. Analysts, regulators, and insurance industry officials said they were puzzled by the seasonal price swings.

“We’re all surprised that there would be that much fluctuation month to month,” said Frank O’Brien, a vice president with the Property Casualty Insurers Association of America, a trade group that advocates for insurance companies.

Although companies can file rate increases throughout the year, many may make them effective Jan. 1, resulting in higher prices in those first few months, O’Brien speculated.

Companies may also adjust their rates to reflect changes in a state’s insurance laws during the year, demographic shifts, or weather events that can trigger more accidents and claims and subsequently higher prices, said Adams of Insurancequotes.com.

But the variations also suggest that consumers should more frequently check auto insurance prices throughout the year, Adams said. Typically, the customer doesn’t face a penalty for switching policies or companies prior to a renewal, she said.

“Consumers really need to be savvy,” Adams said.

Joseph Murphy, the insurance commissioner for Massachusetts agreed. While state officials haven’t studied the report in detail, Murphy said in a statement, the conclusions are correct.

“Drivers are best served by shopping regularly and carefully for car insurance, to confirm that they are receiving the coverage and the price which best fits their personal circumstances,” he said.

Deirdre Fernandes can be reached at deirdre.fernandes@globe.com. Follow her on Twitter @fernandesglobe.
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