Strategic Preemption in a Common Property Resource: A Continuous Time Approach Charles F. Mason Department of Economics University of Wyoming Laramie, WY 82071-3985 and Stephen Polasky Department of Applied Economics University of Minnesota St. Paul, MN 55108 & University Fellow Resources for the Future 1616 P St NW Washington DC 20036 Revised, December 2001 Abstract: The threat of future entry affects the exploitation of common property resources in important ways. An incumbent has a strategic incentive to manipulate the resource stock to deter entry or to harvest more stock prior to entry rather than share the resource with the entrant. It is possible that the threat of potential entry can lead to the extinction of the resource even though actual competition would result in a steady state with a positive stock level. JEL codes: C73, L1, Q2 We thank, without implicating, seminar participants at the Australian National University, Montana State University, Victoria University-Wellington, University of Wyoming, University of Rhode Island, Woods Hole Oceanographic Institution, the 1997 Australasian Econometric Society Meetings and the 1998 Allied Social Science Association Meetings in Chicago, and two referees at this journal for useful comments.