Currently, the fund has a focus on global, consumer-oriented companies like Unilever and Nestlé. Over the last decade or so, the firm was astute at identifying the commodities boom and moved into Canadian resource companies like the nickel producer Inco (which generated a big gain when it was taken over by the Brazilian mining giant Vale). After the financial crisis, the fund shifted away from natural resources, although it still holds some positions.

Mr. Bowen expresses some surprise that his concentrated, buy-and-hold, value-oriented approach is considered so unorthodox among pension fund managers. “It’s pretty much what Warren Buffett does,” he said. “He’s not diversified, either. But practically no one else follows his model. We’re like salmon swimming upstream. The consultants have been trying to wedge their way in here, but after 40 years, the trustees back me.”

Mr. Griner, the pension board vice chairman, said: “Every time I go to a conference, there’s a sales pitch that, the more you diversify the safer you are. But my train of thought is: I’ve got a 40-year return rate here that blows any methodology out of the water. No one else, not the big money managers, not the big endowments, have the same returns with such low fees. We’ve got a history of 20-year rolling returns that’s higher than what the S.&P. is putting out. That’s as solid as you can get. As long as Jay keeps producing those kinds of returns, I can’t fathom changing anything.”

Both Mr. Bowen and Mr. Griner acknowledge that the fund doesn’t always outperform broader averages. Last year, the fund’s return of 15.11 percent qualified for the 14th percentile in the Wilshire Universe, and trailed the S.&P.’s 19.3 percent return over the same period. (The fund’s stocks, however, did outperform the S.&P. 500.) “We have the luxury of taking a long-term approach, Mr. Bowen said. “If we outperformed the S.&P. 500 every year, we’d be doing something wrong.”

Mr. Griner said that a patient, long-term approach is instilled in new trustees by others on the board. (He’s one of nine trustees, which include three each from the fire and police departments and three appointed by the mayor.) “Our fund exists in perpetuity,” he said. “So a three- or one-year outlook, it has some influence, but it’s not going to dictate our outlook. We want growth over 50, 60 years. We want Jay to look long term and give us stable long-term results.”

Michael Schlachter, a managing director at Wilshire Associates, is one of the skeptics about the fund’s approach and its ability to keep generating such high returns. He said that handing all of a pension fund’s assets to a single manager like Mr. Bowen “is extremely unusual and it poses a fair amount of risk. To assume that one firm is the best in every asset category, especially a small firm that no one around here has ever heard of, is extremely risky. What if a bus hits the senior person?”

Mr. Griner said he understood why others were skeptical. “The only real down side to having a single manager is if you have a bad one,” he said. “You think of all the managers. How many can outperform the S.&P. over any period of time? It’s very hard to find anyone with any consistency over a decade who can outperform the S.&P. It’s unheard-of. We happened to have gotten a good one, and he’s done a phenomenal job. But I don’t fault others. It would be scary to entrust everything with one person and hope you’ve gotten the right person.” He added, “I hope it never happens, but if Jay leaves, a low-fee index option might be the way to go.”