Goods Versus Characteristics: Dimension Reduction and Revealed Preference

This paper compares the goods and characteristics models of the consumer within a non-parametric revealed preference framework. Of primary interest is to make a comparison on the basis of predictive success that takes into account dimension reduction. This allows us to nonparametrically identify the model which best fits the data. We implement these procedures on household panel data from the UK milk market. The primary result is that the better fit of the characteristics model is entirely attributable to dimension reduction.Characteristics; demand; dimension reduction; nested models; revealed preference

Goods versus characteristics: dimension reduction and revealed preference

This paper compares the goods and characteristics models of the consumer within a non-parametric revealed preference framework. Of primary interest is to make a comparison on the basis of predictive success that takes into account dimension reduction. This allows us to nonparametrically identify the model which best fits the data. We implement these procedures on household panel data from the UK milk market. The primary result is that the better fit of the characteristics model is entirely attributable to dimension reduction.Characteristics; demand; dimension reduction; nested models; revealed preference.

Revealed Preference in a Discrete Consumption Space

We show that an agent maximizing some utility function on a discrete (as opposed to continuous) consumption space will obey the generalized axiom of revealed preference (GARP) so long as the agent obeys cost efficiency. Cost efficiency will hold if there is some good, outside the set of goods being studied by the modeler, that can be consumed by the agent in continuous quantities. An application of Afriat's Theorem then guarantees that there is a strictly increasing utility function on the discrete consumption space that rationalizes price and demand observations in that space.Generalized axiom of revealed preference; Afriat's Theorem; discrete demand; utility maximization

A lattice test for additive separability

The author gratefully acknowledges financial support from the European Research Council (ERC) under ERC-2009-AdG grant agreement number 249529.We derive necessary and sufficient conditions for a finite data set of price and demand observations to be consistent with an additively separable preference. We do so without imposing concavity on any of the subutility functions or convexity of the budget set a priori, thereby generalizing earlier results. Our simple and intuitive lattice test easily accommodates departures from rationality, or errors, which subsequently facilitates a rich empirical analysis. We apply our econometric techniques to the food consumption of a panel of British households. The primary empirical finding is that additive separability has considerable success in explaining the data.Publisher PD

Revealed preferences over risk and uncertainty

Revised 16 April 2019. Ludovic Renou would like to acknowledge financial support from the French National Research Agency (ANR), under the grant CIGNE (ANR-15-CE38-0007-01).We develop a nonparametric procedure, called the lattice method, for testing the consistency of contingent consumption data with a broad class of models of choice under risk and under uncertainty. Our method allows for risk loving and elation seeking behavior and can be used to calculate, via Afriat's efficiency index, the magnitude of violations from a particular model of choice. We evaluate the performance of different models (including expected utility, disappointment aversion, rank dependent utility, mean-variance utility, and stochastically monotone utility) in the data collected by Choi et al. (2007), in terms of pass rates, power, and predictive success.Publisher PDFPublisher PD

Afriat’s Theorem and Samuelson’s ‘Eternal Darkness’

Suppose that we have access to a finite set of expenditure data drawn from an individual consumer, i.e., how much of each good has been purchased and at what prices. Afriat (1967) was the first to establish necessary and sufficient conditions on such a data set for rationalizability by utility maximization. In this note, we provide a new and simple proof of Afriat’s Theorem, the explicit steps of which help to more deeply understand the driving force behind one of the more curious features of the result itself, namely that a concave rationalization is without loss of generality in a classical finite data setting. Our proof stresses the importance of the non-uniqueness of a utility representation along with the finiteness of the data set in ensuring the existence of a concave utility function that rationalizes the data

2-Deoxy-2-[F-18]fluoro-D-glucose Joint Uptake on Positron Emission Tomography Images: Rheumatoid Arthritis Versus Osteoarthritis

Purpose: Previous positron emission tomography (PET) studies have shown increased 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake in joints of patients with osteoarthritis (OA) and inflamed joints of patients with rheumatoid arthritis (RA). This study compares FDG uptake in joints of RA and OA patients and FDG-uptake with clinical signs of inflammation. Procedures: FDG-PET scans of hands and wrists were performed in patients with RA and primary OA. PET data were compared with clinical data. Results: 29 % of RA joints and 6 % of OA joints showed elevated FDG-uptake. The level of uptake in PET-positive OA joints was not significantly different from that in RA joints. The majority of PET results of RA joints corresponded with clinical findings. Clinical synovitis was found some OA joints with FDG-uptake. Conclusions: FDG-uptake was observed in the majority of clinically inflamed RA joints and in a few OA joints with no significant difference in uptake level. The latter may be due to secondary synovitis

MR Evaluation of Radiation Synovectomy of the Knee by Means of Intra-articular Injection of Holmium-166-Chitosan Complex in Patients with Rheumatoid Arthritis: Results at 4-month Follow-up

Objective To determine whether MRI is able to demonstrate the effect of radiation synovectomy after the intra-articular injection of holmium-166-chitosan complex for the treatment of rheumatoid arthritis of the knee. Materials and Methods Fourteen patients aged 36-59 years were treated with 10-20 mCi of holmium-166-chitosan complex. A criterion for inclusion in this study was the absence of observable improvement after 3- or more months of treatment of the knee with disease-modifying anti-rheumatic drugs. MR images were acquired both prior to and 4-months after treatment. Clinical evaluation included the use of visual analog scales to assess pain, and the circumference of the knee and its range of motion were also determined. MR evaluation included measurement of the volume of synovial enhancement and wall thickness, the amount of joint effusion, and quantifiable scoring of bone erosion, bone edema and lymph nodes. Results Visual analog scale readings decreased significantly after radiation synovectomy (p <0.05). MRI showed that joint effusion decreased significantly (p <0.05), and that the volume of synovial enhancement tended to decrease, but to an insignificant extent (p = 0.107). Conclusion The decreased joint effusion noted at 4-month follow-up resulted from radiation synovectomy of the rheumatoid knee by means of intra-articular injection of holmium-166-chitosan complex.ope