William W. Behrens III was a doctoral student at mit-system-dynamics-group under jay-forrester and a member of the team that produced limits-to-growth-1972. He is the fourth co-author of the original 1972 study, alongside Donella Meadows (lead author), dennis-meadows (project director), and jorgen-randers.
Behrens contributed to the development and calibration of the World3 model that underlies the Limits study. The World3 model incorporated five interacting subsystems — population, food production, industrial output, pollution, and nonrenewable resources — and Behrens's technical work on the model was part of the collaborative research effort the club-of-rome commissioned.
Unlike the other three co-authors, Behrens did not continue as a co-author on the subsequent updates (beyond-the-limits-1992 and limits-to-growth-30-year-update-2004). He is also substantially less visible in the public reception of the Limits project, which centered on Donella Meadows as lead author and communicator. His lower importance rating reflects this reduced public profile and the absence of a continuing independent career in systems thinking or sustainability science parallel to those of Randers or Dennis Meadows.
Behrens's role is nonetheless historically significant: the four-author team of limits-to-growth-1972 should be credited collectively. The tendency to attribute the book primarily to Donella Meadows alone (or sometimes to Dennis Meadows) obscures both Randers's and Behrens's contributions to the original modeling work.
The mit-and-limits-to-growth-1970-1972 era was the context for Behrens's collaboration with Meadows. Within that era, he represents the team's technical capacity at the doctoral student level — the collective effort that made the World3 model possible.