Susan Hirt Hagen, the daughter of Henry Orth Hirt, one of the pioneers of the car insurance industry, has been a billionaire for years -- and has never appeared on an international wealth ranking.

Hagen has a net worth of $1.7 billion, according to the Bloomberg Billionaires Index. Shares of Erie, Pennsylvania-based insurer Erie Indemnity Co., the third-largest auto insurer in Pennsylvania, have doubled in the past three years. The 76-year- old controls the majority of the company’s voting stock and 35 percent of its common shares.

“Erie is not a traditionally structured insurance company,” Jonathan Adams, a senior insurance analyst with Bloomberg Industries in Princeton, New Jersey, said by phone. “It has very little exposure to underwriting risk. You have to hand it to the family; it’s a very clever approach.”

Surging U.S. auto sales resulted in a 6.1 percent jump in auto insurance prices in December, according to data compiled by Bloomberg. That is boosting shares of U.S. property and casualty insurers, which have gained almost 6 percent the past month, almost double the advance by the Standard & Poor’s 500 Index.

Hagen’s stake in Erie is valued at $1.4 billion. She has also earned more than $400 million in dividends since 1991.

Leah Knapp, an Erie Indemnity spokesman, said Hagen declined to comment on her net worth.

Family Partnership

According to the company’s 2012 proxy statement filed with the U.S. Securities and Exchange Commission, Hagen controls 16.8 million non-voting Class A shares and 1,339 voting Class B shares. The shares are held in her name, by her husband, Erie chairman Thomas B. Hagen, and in a family partnership and a trust she is the beneficiary of.

Each Class B share is convertible into 2,400 Class A shares. Erie closed at $69.63 yesterday, up 11.9 percent from their 23-month low of $62.22 in October.

H.O. Hirt co-founded Erie Exchange in 1925. The company was one of the first in the U.S. to offer auto insurance, selling premiums for $34 in its first year. He expanded in the following decades to offer fire insurance, inland marine insurance and life insurance.