NETWORK LOADING VERSUS EQUILIBRIUM ESTIMATION OF THE STOCHASTIC ROUTE CHOICE MODEL MAXIMUM LIKELIHOOD AND LEAST SQUARES REVISITED*

Daganzo (1977, 1979), Daganzo and Sheffi (1977), Sheffi (1985), and Sheffi and Daganzo (1980) have used one assumption about traveler behavior in developing estimation techniques for the stochastic route-choice problem and another assumption in predicting flows on networks by using the same model. In estimation, they calculate the congested travel costs of the network links from observed flows on the network, and the network is loaded based on these costs. In prediction, they follow their stochastic user-equilibrium assumption by which travelers evaluate costs using the mean of the observed flows (or equilibrium flows). The travel-cost coefficient obtained from the loading method systematically overestimates the true travel-cost coefficient from which the observed flow data (which must be used in loading) is generated. The estimates of the same coefficient, obtained in this paper, by constraining the estimation results to conform to the equilibrium conditions are unbiased, and only marginally less efficient (have larger standard deviations). The average percentage error and inefficiency of the link flow predictions based on the loading method increases as the level of congestion on the network rises. In contrast, the average percentage error of link flow predictions based on the equilibrium estimation method declines and their efficiency remains very high as the level of congestion on the network rises.     

Representing Structural Change in U.S. Migration Patterns

This paper focuses on the identification of three sets of relationships exhibited by a time series of age-specific national migration rates and multiregional transition probability matrices: the relationship across time for the same age group, as defined by period (temporal) transformation coefficients or matrices; the relationships across age at a particular moment in time, as defined by age transformation coefficients or matrices; and the relationships across time and age, as defined by cohort transformation coefficients or matrices. Given any two of these relationships one can solve for the third. This feature of age-period-cohort relationships has a practical application in the development of improved methods for representing structural change in migration patterns over time and for indirectly estimating migration patterns using inadequate data.     

Explaining A Paradox: The Alberta-California Natural Gas Trade Dispute

For over 3 years the Alberta government and the California Public Utilities Commission engaged in a bitter dispute over the future of the Alberta-California natural gas trade. This article examines how both sides sought to use their regulatory authority to control the substance of gas trade restructuring. It assesses the dispute as an exercise in deregulatory policymaking and suggests the need for increased study of the role and motivations of subnational regulatory actors.     

Inward investment and economic development in Poland

This paper summarizes results of a research project funded by the Overseas Development Administration of the UK Government. Its aims were to explore the nature and extent of foreign direct investment in Poland, and to assess the extent of integration of such investment with the indigenous economy. The research involved interviews with Polish government ministries, banks, development agencies, inward investors and indigenous firms. It concludes that there are numerous financial and technical obstacles to indigenous business development. The majority of inward investors aim to serve the Polish and other Central and Eastern European markets rather than simply selling cheaply produced products to the West. Moreover, most have already developed significant local sourcing from Polish suppliers.     

The changing pattern of urban fertility in Eastern Australia 1966-1976

This paper uses unpublished data from official sources to analyze variations in urban marital and overall fertility in Eastern Australia between 1966-71 and between 1971-76. It further attempts to assess the relevance of the convergence thesis to changing fertility patterns and to evaluate the utility of an ecologic analysis of interurban fertility differences. The data indicate that urban fertility levels declined dramatically in 1966-76 and interurban differentials were substantially reduced. By 1976, the 2-child family norm had been widely adopted throughout Australia, regardless of region, community size, or sociocultural composition. Examination of marital fertility trends suggests that, although different areas had different elasticities of response to cyclical fertility movements in the 1960s, the magnitude of these differences was insufficient to do more than slow the pace of the decline while increasing the pace of interarea differential convergence. Declines in both proportions married and marital fertility after 1971 were reflected in declining overall fertility in all urban areas in Eastern Australia. During this period, however, divergence replaced the convergence evident in the 1960s. The present high level of uniformity in both marital and overall fertility rates throughout the study area about mean levels means that the regionally variable effects of future cyclical changes in fertility levels may be difficult to identify. As a result, detailed analyses at the individual/behavioral level that focus specifically on attitudes, values, and family size preferences may be more appropriate for understanding of post-transitional demographic change than studies based on spatial analyses at the local level.