More consumers are resistant to signing up for driver-monitoring programs in exchange for potential discounts on their car insurance, according to a study released this week.

According to insuranceQuotes.com, 51 percent of Americans say they wouldn’t consider enrolling in a pay-as-you-drive insurance plan, which also is called usage-based insurance or telematics.

That’s up from the 37 percent last year who said they wouldn’t consider enrolling in such a program, said insuranceQuotes.com.

State Farm, Allstate and Progressive are among the car insurers offering potential discounts to policyholders who sign up for programs that track driving behavior. A device installed in the car is one way that the information is gathered for the insurer. Typically, the insurers have said they use the information to reward good drivers, not penalize bad ones.

The percentage of consumers who have or have had usage-based insurance policies is small: 8 percent as of July 2014, according to a survey of 1,000 U.S. consumers by Towers Watson, a consulting firm.

Still, that’s nearly double the percentage in February 2013.

Millennials are most likely to sign up for pay-as-you-drive insurance and least concerned about related privacy issues, insuranceQuotes.com found.

Of the respondents who wouldn’t consider signing up for pay-as-you-drive insurance, 21 percent said the main concern was sharing personal information.