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Gattini, Luca. "QUALITY MEASUREMENT AND QUALITY IN PRICES INDEXES", Università Cattolica del Sacro Cuore, XXI ciclo, a.a. 2008/09, Milano, [http://hdl.handle.net/10280/674].

Language: ENG
English Abstract: Rapid technical progress has increased the speed of quality change. Its impact has a large scale effect on a broad set of variables and it has exacerbated a latent economic problem on the measurement of true economic variables. For example, the reliability of the Consumer Price Index (CPI) has been increasingly undermined since it has been argued that price indexes suffer either an upward or a downward bias due to quality change in goods and services. This paper is aimed to be a comprehensive survey on historical contributions to modeling quality from a theoretical perspective. The fundamental contributions of several economists are framed into a coherent building block. We construct a general framework for quality adjustment in price index theory which helps to understand the importance of economic theory for price index definitions. Supply and demand side models are analysed and merged into Rosen (1974) model, the first well grounded attempt to construct a general equilibrium explanation to quality choices. First, we address the issue of quality measures into price index theory. Then, we present a survey of the relevant contributions to hedonic price modeling. We focus on two main fields of applied analysis: (1) determining how the price of a unit of commodity varies with the set of attributes; (2) estimating the demand and supply functions for the attributes of products. The open issues on quality adjustment in consumer price indexes will be analysed in the two applied papers, namely chapter 3 and chapter 4. They are two applied original contributions to hedonic price literature. Chapter 3: In this paper we show that a real time measure of pure price change for different varieties of non durable volatile and seasonal products is possible. Moreover, we introduce the idea of unobservable elements captured by brand specific and by time specific dummies. In order to compute a pure price index, a theoretically correct quality adjustment procedure has been determined where quality is measured in terms of attributes (Griliches, 1971a, 1971b; Tauchen and Witte, 2001; Pakes, 2003; Ekeland et al. 2002, 2004; Triplett 2004) and it is becomes a ’fundamental’ of the market. We have analyzed the prices of apples and oranges traded in the General Milan Market for fruit and vegetables. We have used a large amount of information from more than 8000 of observations collected between 2000 and 2004. We have found that quality is changed over time even if new goods/varieties were not introduced. Price levels adjusted for qualitative levels, measured in terms of the content of characteristics, are above the Laspeyres hedonic price index on average for apples whilst the pure price index for oranges is close to the Laspeyres price index. Our empirical analysis shows that a price index, which does not account for quality change, is underepresiting inflation for apples and correctly measuring price changes for oranges. Chapter 4: The relevant literature dealing with the problem of quality measurement in passenger cars (inter alias, Ohta and Griliches 1976, 1983; Lancaster (1966), Rosen (1974), Berry et al. 1995; 2004) relies on general hedonic imputation methods for the assessment of the quality adjusted price index. We deviate from this standard approach by computing a new quality adjusted index for cars based on a weighted adjustment procedure which accounts for attrition due to observable elements (Fitzgerald et al., 1998; Nevo, 2003; Horowitz and Manski, 1998). By doing this, we are able to define a quality adjusted price index which generates a more accurate identification of price index levels than the current state of the art. We use data for the universe of new cars and their characteristics, sold between 2000 and 2007 in Italy, and we identify the basic reference unit. Based on this we study the pricing behavior of the firms. We model a non random and non ignorable selection process based on an entry/exit process of cars (Olly and Pakes, 1996) due to profit maximizing firms in a differentiated product space. We find that the official index is overestimating inflation since our results point to a mild deflation. However we show that traditional hedonic techniques lead to an overestimation of quality improvement and consequently they under-estimate inflation.
Defense Date: 3-Feb-2010
URI: http://hdl.handle.net/10280/674

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