I just learned that Jack Knetsch died back in August. Here is the obituary from Simon Fraser University:
Jack was a Professor in SFU’s Economics Department and the School of Resource and Environmental Management from 1974 to 1998, at which time he transitioned to Professor Emeritus. Jack received his PhD from Harvard University and worked at Resources for the Future in Washington, DC, before coming to SFU.
Jack was an excellent teacher, mentor and colleague, but he especially made his mark through contributions to leading economics research. With co-authors like Daniel Kahneman, Jack’s experimental research challenged some of the key underlying assumptions of neoclassical economics, with significant implications for the methods used to estimate the monetary value of environmental losses. He had over 200 publications, with many of these in the top economics journals. And some of his collaborators (Kahneman, Thaler) were eventually recognized with the Nobel Prize for the innovative research path to which Jack contributed.
Here is a link to a 1968 book review of the Clawson and Knetsch’s 1966 Economics of Outdoor Recreation: Review of Clawson and Knetsch Economics of Outdoor Recreation (PDF). Hotelling is credited with the suggestion for the travel cost method but it was Clawson and Knetsch (1966) who figured out how to do it.
He was still conducting research in his late 80s. Here is the Google Scholar page for publications since 2019: https://scholar.google.com/scholar?as_ylo=2019&q=jack+knetsch&hl=en&as_sdt=0,34.