WASHINGTON — Striking new evidence has emerged of a widespread gap in the cost of health insurance, as women pay much more than men of the same age for individual insurance policies providing identical coverage, according to new data from insurance companies and online brokers.

Some insurance executives expressed surprise at the size and prevalence of the disparities, which can make a woman’s insurance cost hundreds of dollars a year more than a man’s. Women’s advocacy groups have raised concerns about the differences, and members of Congress have begun to question the justification for them.

The new findings, which are not easily explained away, come amid anxiety about the declining economy. More and more people are shopping for individual health insurance policies because they have lost jobs that provided coverage. Politicians of both parties have offered proposals that would expand the role of the individual market, giving people tax credits or other assistance to buy coverage on their own.

“Women often fare worse than men in the individual insurance market,” said Senator Max Baucus, Democrat of Montana and chairman of the Finance Committee.