Hägerstrand, Torsten (1916–2004)

Torsten Hägerstrand was a Swedish geographer who made enormous contributions to human geography. The work that initially established his international reputation and his place as one of the most renowned human geographers of the 20th century concerned the study of population movements over time, the diffusion of innovations, and the behavior of individuals in space and time. Innovation indeed well describes his role in geography, in perhaps four ways: first, the introduction (at least to geography) of the idea of spatial and space-time processes, that geographic development over time could be understood and modeled; second, the particular process of spatial diffusion; third, the technique of Monte Carlo simulation; and fourth, the idea that individual behavior, not just that of large groups, could be modeled temporally and spatially. All were revolutionary. And underlying all these was the conviction that geography could offer integrated perspectives, transcending the boundaries of the humanities and sciences. His early work already insisted on the necessity of construction of theory and the responsibility of testing and evaluating empirical evidence.

Hägerstrand was born in Moheda, Sweden, and was perhaps destined to become a geographer: Even as a child, he explored and mapped his surroundings! He moved to Lund in 1937, where he studied, taught, conducted research on [Page 1398]migration, and completed his licentiate in 1947. In this period, he was profoundly influenced by Edgar Kant (a refugee from the University of Kartu in Estonia) in the role of theory and method in scientific geography. His PhD dissertation was completed in 1953 but was not translated into English until 1966, by Alan Pred as Innovation Diffusion as a Spatial Process. This work was unabashedly theoretical and quantitative, when geography in the United States and in the United Kingdom was almost universally idiographic. In 1957, his extended article (based on the licentiate research) “Migration and Area” was published in English, also a pioneering and brilliant contribution to the analysis of migration. But it was not until 1959, at the urging of Bill Garrison, that the University of Washington invited Hägerstrand as a visiting professor. The students, budding exponents of a theoretical and quantitative geography, were excited and inspired by the novelty and brilliance of his ideas, which led to a rapid and enthusiastic dissemination of innovation diffusion theory and methods. The process was furthered by the success of the Lund Symposium in Urban Geography in 1960 and by Hägerstrand's participation in the National Science Foundation Quantitative Methods workshop at Northwestern University in 1961.

Although Hägerstrand's approach was theoretical, quantitative, and devoted to formal modeling, it differed from the dominant early work derived from spatial economics in four basic, indeed revolutionary ways: (1) his goal was to understand spatial processes unfolding over time; (2) the unit of study was the individual or household, not population per se; (3) the processes studied were more social and cultural than economic; and (4) and this required probabilistic rather than deterministic mathematics. The spatial diffusion framework has had enormous subsequent influence within geography and beyond (communications, history, epidemiology, anthropology, even economics). Within geography, perhaps the most influenced was Allan Pred, who translated Hägerstrand's dissertation and did work on urban diffusion and later time-geography. The evaluation of spatial diffusion also required advances in spatial statistics.

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