In the final part of this four-part series, economic limits for offshore structures in the Outer Continental Shelf (OCS) Gulf of Mexico (GOM) are computed.We classify 1,962 decommissioned structures between 1986-2009 by structure type, primary production, water depth, and year of removal, and compute production, adjusted gross revenue, and water cut thresholds near the end of their life cycle.Production and gross revenue provide direct information on economic limits and the commercial status of operations. Water production is an important parameter because the disposal of produced water costs money, and as water production increases so does operating expense.During the last year of produc...