Herrick and Squires Measuring fishing fleet productivity 



89 



Because the U.S. tropical tuna purse-seine fleet oper- 

 ates almost exclusively in the Pacific Ocean, resource 

 abundance measures relied on the extensive biological 

 database that has been compiled by the Inter-American 

 Tropical Tuna Commission (lATTC, La Jolla, CA 

 92038). From the lATTC database, we obtained esti- 

 mates of annual yellowfin tuna biomass and estimates 

 of catchability coefficients for yellowfin in the Commis- 

 sion's eastern tropical Pacific yellowfin regulatory area 

 (CYRA). The CYRA was the only region of the Pacific 

 for which such data were available. Moreover, there 

 were no such data for skipjack tuna from any area of 

 the Pacific. Because of these circumstances, it was not 

 possible to explicitly account for fluctuations in biomass 

 over the full range of the fishery and across all species 

 harvested. Therefore, only the annual yellowfin bio- 

 mass in the CYRA weighted by the catchability coeffi- 

 cient was used to adjust fleet productivity for changes 

 in resource abundance. 



Empirical results 



Table 1 reports changes in annual total-factor produc- 

 tivity growth for the U.S. tropical tuna fleet over the 

 period 1981-85 using Tornqvist bilateral-chain indices. 

 Each of the total-factor productivity growth rates pre- 

 sented in Table 1 is distinguished by its specification 

 of the capital input and adjustments for changes in re- 

 source abundance. Treatment of outputs and the other 

 inputs is the same in all cases. To anticipate our results, 

 we find that adjusting the traditional productivity mea- 

 sures for variations in economic capacity utilization and 

 changes in resource abundance pares away sources of 



output growth that are not due to technical progress, 

 giving a more accurate measure of productivity. 



Productivity measures under full equilibrium 



Columns (1) and (2) of Table 1 provide productivity 

 growth measures assuming long-run equilibrium— eco- 

 nomic capacity is fully utilized— without accounting for 

 changes in resource abundance. The total factor pro- 

 ductivity growth rates in column (1) use the first capital 

 index: capital is represented by the number of vessels 

 included in the fleet. The growth rates reported in col- 

 umn (2) are based on the second capital index: capital 

 is represented by the carrying capacity of the fleet. 

 Because vessels leaving the fleet during the period 

 tended to be older and in the smaller size-categories, 

 capital expressed in number of vessels decreased at a 

 greater rate than capital measured in aggregate car- 

 rying capacity (columns [2] and [3] of Table 2). Hence, 

 total-factor productivity growth based on the second 

 capital index is lower than that based on the first capital 

 index for those years in which the fleet declined.' 



'It might be argued that technical progress is embodied in the capital 

 stock, so that different ages of vessels, embodying different advances 

 in technical progress, should be ex[3licitly considered. Tliis is referred 

 to as vintage effects, and is certainly the case for some types of 

 technical progress such as purse seining versus pole-and-line 

 harvesting. However, in recent years, much of the technical pro- 

 gress has been in the form of vessel electronics. While this type of 

 technological change in a narrow sense, represents embodied tech- 

 nical change, so that vintage effects could theoretically be impor- 

 tant, the volume of investment is negligible in comparison with the 

 vessel's value, and much of the technical change is fundamentally 

 related to the managerial function, information, and learning-by- 

 doing: Hick's-neutral technical change. 



