Millions of people will see price changes on their next insurance policy following fresh rules that have now come into force.
New European rules mean insurers will no longer be able to take a customer's gender into account when calculating their premiums.
The changes mean that young women may see their car insurance costs rise.
But they could get a better deal when buying an annuity - an annual pension financed by their private pension pot.
The changes, which came into force on Friday, are the result of a ruling from the European Court of Justice (ECJ) in March last year.
Premiums must now be "gender neutral", with men and women being treated the same, even if they present obviously different risks to insurers.
Previously, women have benefited from smaller vehicle insurance premiums because they account for fewer accidents.
"The youngest drivers will be most affected. That is because young men are more than twice as likely to be killed or seriously injured in a car crash than their female peers," said Ian Crowder, spokesman for AA Insurance which monitors quotes across the industry.
"Young women aged 17 to 22 typically pay up to 40% less for their cover than young men; well, until now at any rate. In middle age, there is little difference in premiums between the genders."
Premiums were dropping by up to 10% for men aged 25 and below and were increasing by up to 30% for the youngest women drivers, Mr Crowder said.
An annual pension income - or annuity - that people can buy from an insurance company could be affected by the change. Previously, women's annuities were not so generous as men's owing to their extra life expectancy.
Life insurance and health insurance premiums could also be affected by the new rules.
Prices are likely to change in stages as the new system beds in, and insurers analyse what their competitors are doing.
The Association of British Insurers has suggested that people shop around for the most suitable deal, and do not focus solely on price.