Heteroskedasticity-Consistent Estimation of the Variance-Covariance Matrix for the Almost Ideal Demand System

In this note I demonstrate the previously overlooked fact that if the AIDS aggregate demand model is constructed as the aggregation of individual consumer demands, then the error structure for any individual equation is necessarily heteroskedastic unless the distribution of income is constant across aggregates. Maximum likelihood estimation which ignores this heteroskedasticity yields inconsistent estimates of the variance-covariance matrix and renders likelihood ratio tests of the restrictions of consumer demand theory inappropriate. A heteroskedasticity-consistent estimator of the variance-covariance matrix is proposed by adopting the technique of White (1980) to the case at hand.

Productivity Growth in the Automobile Industry, 1970-1980: A Comparisonof Canada, Japan and the United States

In this paper we calculate and analyze the automobile industries cost and productivity experience during the 1970 's in Canada, the U.S.and Japan. Utilizing an econometric cost function methodology, we are able to isolate the major source of short-run disequilibrium in this industry-variations' in capacity utilization-and analyze its effects on cost and total factor productivity (TFP) gross. This is achieved through a novel application of the Viner-Wng envelope theorem, which allows us to track short-run behavior utilizing what is essentially a long-run cost function.To striking empirical results energe. First, TFP grew much faster in the Japanese automobile industry (4.3% annum) than in the Canadian (1.4%) and U. S.(1.6%) industries. Second, the importance in analyzing variations in capacity utilization is confinned by the fact that failure to correct for this source of productivity change would have led to a 31% under estimate of long-run TFP growth in Canada arid a 37% underestimate for the United States.

The Extent and Sources of Cost and Efficiency Differences Between U.S. and Japanese Automobile Producers

In this paper we present for the first time estimates of cost and efficiency differences between U.S. and Japanese producers based on an econometric cost function methodology rather than the accounting frameworks previously used. We demonstrate that the cost difference estimates for 1979 which were influential in the debate that resulted in the Voluntary Restraints Agreements of 1981-85 were substantial over estimates of the Japanese advantage. While our estimate of the Japanese cost advantage for 1980 is similar to previous estimates, we attribute most of this advantage to short-run phenomena -underutilization of U.S. production capacity and an undervalued yen. In a previous paper we have shown that the Japanese TFP growth rate was much faster than the U.S. rate during the 1970's. However we estimate the long-run underlying Japanese efficiency advantage as of 1980 to have been only 1-2%, much less than previously estimated. This results from the fact that Japan began the 1970's with a long-run efficiency disadvantage of over 20%, and the decade of the 1970's represented a catch-up period for Japanese producers.

DNA charge transport as a first step in coordinating the detection of lesions by repair proteins

Damaged bases in DNA are known to lead to errors in replication and transcription, compromising the integrity of the genome. We have proposed a model where repair proteins containing redox-active [4Fe-4S] clusters utilize DNA charge transport (CT) as a first step in finding lesions. In this model, the population of sites to search is reduced by a localization of protein in the vicinity of lesions. Here, we examine this model using single-molecule atomic force microscopy (AFM). XPD, a 5′-3′ helicase involved in nucleotide excision repair, contains a [4Fe-4S] cluster and exhibits a DNA-bound redox potential that is physiologically relevant. In AFM studies, we observe the redistribution of XPD onto kilobase DNA strands containing a single base mismatch, which is not a specific substrate for XPD but, like a lesion, inhibits CT. We further provide evidence for DNA-mediated signaling between XPD and Endonuclease III (EndoIII), a base excision repair glycosylase that also contains a [4Fe-4S] cluster. When XPD and EndoIII are mixed together, they coordinate in relocalizing onto the mismatched strand. However, when a CT-deficient mutant of either repair protein is combined with the CT-proficient repair partner, no relocalization occurs. These data not only indicate a general link between the ability of a repair protein to carry out DNA CT and its ability to redistribute onto DNA strands near lesions but also provide evidence for coordinated DNA CT between different repair proteins in their search for damage in the genome

ATP-Stimulated, DNA-Mediated Redox Signaling by XPD, a DNA Repair and Transcription Helicase

Using DNA-modified electrodes, we show DNA-mediated signaling by XPD, a helicase that contains a [4Fe-4S] cluster and is critical for nucleotide excision repair and transcription. The DNA-mediated redox signal resembles that of base excision repair proteins, with a DNA-bound redox potential of ~80 mV versus NHE. Significantly, this signal increases with ATP hydrolysis. Moreover, the redox signal is substrate-dependent, reports on the DNA conformational changes associated with enzymatic function, and may reflect a general biological role for DNA charge transport

Productivity measurement using capital asset valuation to adjust for variations in utilization

Also released as Working Paper No. 8125, Institute for Policy Analysis, University of Toronto. *An earlier version was presented at the econometric Society Summer Meetings, San Diego, California, June 24-27, 1981.Although a great deal of empirical research on productivity measurement has taken place in the last decade, one issue remaining particularly controversial and decisive is the manner by which one adjusts the productivity residual for variations in capital and capacity utilization. In this paper we use the Marshallian framework of a short run production or cost function with certain inputs quasi-fixed to provide a theoretical basis for accounting for variations in utilization. The theoretical model implies that the value of services from stocks of quasi-fixed inputs should be altered rather than their quantity. This represents a departure from previous procedures that have adjusted the quantity of capital services for variations in utilization. In the empirical illustration, we employ Tobin's q to measure the shadow value of capital, and find that for the U.S. manufacturing sector, we can attribute 25% of the traditionally measured decline in productivity growth during 1973-77 to a decline in capacity utilization.Research supported by the Department of Energy, under Contract EX-76-A-Ol-2295, Task Order 67

Principals' Perceptions of Changing the Age=Grade Traditional Model of Schooling

The traditional education system has roots in the colonial and industrial eras, but the purpose of education in today's dynamic and global economy has vastly changed. Schools need to produce creative thinkers and problem solvers. This research reviewed existing literature to explore the intersections of multiage learning, mastery learning, and blended learning in elementary schools. Centered on research questions that examined principals' perceptions of moving to a new model of elementary schooling that breaks down the barriers of age = grade (students placed into classroom because of their age) traditional schooling, this study sought to support the implementation of instructional strategies to meet elementary students' needs in the digital age. A phenomenological qualitative research design was used for the study. Six elementary school principals in schools that have implemented some aspects of multiage learning, mastery learning, and blended learning were interviewed to construct a description of their experience of breaking down the barriers of age = grade traditional elementary schooling. The findings showed that teacher capacity, progression of the curriculum, technology, time/master scheduling, and principal/teacher readiness for change emerged as barriers to moving to a new model of elementary schooling. Many conclusions were revealed in the data, but perhaps the most important was that barriers to changing the age = grade model of elementary schooling are not insurmountable. This study showed that there is a willingness and eagerness to make changes to the traditional age = grade elementary school model to meet the needs of students in the digital age.Ed.D., Educational Leadership and Management -- Drexel University, 201