Robert W. Fogel, a Nobel Prize-winning economic historian who used empirical data in innovative and iconoclastic ways, most notably to dispute longheld assumptions about why slavery collapsed as an institution in the United States, died June 11 at a rehabilitation facility in Oak Lawn, Ill. He was 86.

The cause was pneumonia, said his daughter-in-law Suzanne Fogel. Dr. Fogel, a Chicago resident, spent much of his career at the University of Chicago and directed its Center for Population Economics.

Dr. Fogel shared the 1993 Nobel Prize for Economic Sciences with Douglass North, then of Washington University in St. Louis. Both winners were on the 1960s vanguard of a field known as cliometrics, which merges economic theory with statistical analysis of hard numbers raked from the past; Clio is the muse of history in Greek mythology....