Rex Sinquefield, who 24 years ago co-founded Dimensional Fund Advisors and served as its co-chair and chairman of investment policy, will retire at the end of the year, the fund company announced.
   Sinquefield, an iconic and sometimes outspoken proponent of passive investment and efficient market theory, will retire to his farm in Missouri and pursue a variety of interests, including the creation of an economic think tank, Dimensional Fund Advisors said.
   Sinquefield's wife, Jeanne, who has supervised the company's trading operation since 1983, will also retire at the end of the year, the company announced.
   Rex Sinquefield founded Dimensional in 1981 with David Booth with the aim of applying academic research to investment management. Much of DFA's work is tied to research conducted at the University of Chicago, where Booth and Sinquefield attended graduate school. The underpinnings of the company's philosophy include a belief in efficient markets and passive investment.
   When it comes to the passive vs. active schools of investment theory, in fact, both Booth and Sinquefield have been blunt about their disregard for active management, market timing, stock picking and other similar endeavors. Sinquefield once called active management a form of "investment pornography."
   DFA has about $70 billion under management for more than 300 clients, including high-net-worth investors through professional financial advisors, the company says. Its board members and consultants include Eugene Fama of the University of Chicago, Nobel Laureates Myron Scholes and Robert Merton, Kenneth French of Dartmouth College and Robert Ibbotson of Yale University.
   Sinquefield will remain a board member and consultant to the company after his retirement, according to DFA.
   "Rex and Jeanne are good friends and dear colleagues whose talents will remain an important resource for years to come," said Booth, DFA's co-chair and chief investment officer.