Long-Run Structural and Productivity Change in U.S. Agriculture: Effects of Prices and Policies

Long-Run Structural and Productivity Change in U.S. Agriculture: Effects of Prices and Policies by Wallace E. Huffman and Robert E. Evenson The paper presents (1) a conceptual framework for structural change when farms may be multiproduct or specialized and (2) an econometrics examination of causes of structural and total factor productivity (TFP) change for U.S. agriculture. Farm size, farm specialization, and part-time farming are the structural dimension emphasized, and they become potential channels to TFP change. Using state aggregate data starting in 1950, we conclude that input prices, public and private research, public extension, and government commodity programs have directly and indirectly caused change in U.S. farm structure and TFP. Our results suggest that changes in farm size, however, have been dominated by input price changes rather than by technology or government programs.farm structure, productivity, farm size, farm specialization, part-time farming, research, technical change, agriculture

The Quest for Purchasing Power Parity with a Series-specific Unit Root Test Using Panel Data

A unit root testing procedure is presented that exploits the well-established power advantages of panel estimation while rectifying a deficiency in other panel unit root tests. This procedure, which takes into account contemporaneous cross-correlation and heterogeneous serial correlation of the regression residuals, allows determination of which members of the panel reject the null hypothesis of a unit root and which do not. Applying the procedure to real exchange rates yields results that are in broad agreement with those obtained from single-equation unit root tests. There is little evidence that a unit root can be rejected in dollar-based real exchange rates for the floating rate period.Marketing,

Status of major southern California marine sport fish species with management recommendations, based on analyses of catch and size composition data collected on board commercial passenger fishing vessels from 1985 through 1987

This report on the status of major southern California marine sport fish species, together with management recommendations, is based on analyses of catch and size composition data, which were collected on board Commercial Passenger Fishing Vessels (CPFV) from 1985 through 1987. The project was designed to determine the status of those fishes that support the CPFV industry, and to make management recommendations when deemed necessary. We collected and analyzed data based on random, stratified, on-board sampling of weekday (excluding holidays), open CPFV's on a year-round basis. We sampled 1/2-day, 3/4-day, and full-day type trips at a level of 5%. The survey area extended from below the United States-Mexican border to Point Arguello. Catch estimates were extrapolated to include weekday as well as weekend and holiday, open and chartered CPFV's. We sampled 736 CPFV trips in 1985, 650 in 1986, and 631 in 1987. We encountered 180 species of fishes, including 49 species of rockfishes. We performed detailed analyses on 14 non-rockfish species and 12 rockfish species, as well as all fishes as a group and all rockfishes as a group. We found a moderate increase in total catch of combined fish species between this study and one in the mid-1970's, due primarily to sizeable increases in catches of Pacific mackerel, kelp bass, barred sand bass, and barracuda. However, we also found that there has been more than a 50% decline in the CPFV rockfish catches, due primarily to substantial decreases in catches of bocaccio, chilipepper, and olive rockfish. We have recommended that the current 15-rockfish bag limit regulation be reduced to a 10-rockfish bag limit, and that additional and equitable conservation measures also be implemented on the commercial rockfish fishery. (385pp.

Efficient Universal Noiseless Source Codes

Although the existence of universal noiseless variable-rate codes for the class of discrete stationary ergodic sources has previously been established, very few practical universal encoding methods are available. Efficient implementable universal source coding techniques are discussed in this paper. Results are presented on source codes for which a small value of the maximum redundancy is achieved with a relatively short block length. A constructive proof of the existence of universal noiseless codes for discrete stationary sources is first presented. The proof is shown to provide a method for obtaining efficient universal noiseless variable-rate codes for various classes of sources. For memoryless sources, upper and lower bounds are obtained for the minimax redundancy as a function of the block length of the code. Several techniques for constructing universal noiseless source codes for memoryless sources are presented and their redundancies are compared with the bounds. Consideration is given to possible applications to data compression for certain nonstationary sources