NEW YORK – Berkshire Hathaway Inc.’s Warren Buffett, the 79-year-old CEO, is losing an emergency stand-in with the retirement of money manager Lou Simpson.

Simpson, who picks stocks at Berkshire’s Geico car insurance unit, plans to leave his position at the end of the year, Debbie Bosanek, an assistant to Buffett, said in an e-mail. The retirement strips Buffett of an executive he has called a “Hall of Fame” investor as the billionaire prepares Omaha, Neb.-based Berkshire for his own eventual departure.

Buffett brought Simpson, 73, to Berkshire with the 1996 acquisition of Geico and touted the new arrival as a backup to handle Berkshire’s investments in the event of an emergency. Simpson’s equity portfolio at Geico posted an average annual gain of 20 percent in the 25 years to the end of 2004, according to that year’s annual report. Buffett manages investments for Berkshire’s other insurance subsidiaries.

Buffett, who oversees an equity portfolio of about $55 billion and more than 70 operating units, plans to have his responsibilities split among more than one manager when he retires. Successors have not been named.