Publications of Koren, M.

Economies of scale and the size of exporters

Exporters are few-less than one-fifth among U.S. manufacturing firms-and are larger than non-exporting firms-about 4-5 times more total sales per firm. These facts are often cited as support for models with economies of scale and firm heterogeneity as in Melitz (2003). The authors find that the basic Melitz model cannot simultaneously match the size and share of exporters given the observed distribution of total sales. Instead exporters are expected to be between 90 and 100 times larger than non-exporters. It is easy to reconcile the model with the data. However, a lot of variation independent of firm size is needed to do so. This suggests that economies of scale play only a minor role in determining a firm's export status. The authors show that the augmented model also has markedly different implications in the event of a trade liberalization. Most of the adjustment is through the intensive margin and productivity gains due to reallocation are halved.

Pricing to firm: an analysis of firm- and product-level import prices

We use Hungarian Customs data on product-level imports of manufacturing firms to document that the import price of a particular product varies substantially across buying firms. We relate the level of import prices to firm characteristics such as size, foreign ownership, and market power. We develop a theory of “pricing to firm” (PTF), where markups depend on the technology and competitive environment of the buyer. The predictions of the model are confirmed by the data: import prices are higher for firms with greater market power, and for more essential intermediate inputs (with a high share in material costs). We take account of the endogeneity of the buyer’s market power with respect to higher import prices and unobserved cost heterogeneity within product categories. The magnitude of PTF is big: the standard deviation of price predicted by PTF is 21.5%.

Volatility and Development

Why is GDP growth so much more volatile in poor countries than in rich ones? We identify three possible reasons: (i) poor countries specialize in fewer and more volatile sectors; (ii) poor countries experience more frequent and more severe aggregate shocks (e.g., from macroeconomic policy); and (iii) poor countries' macroeconomic fluctuations are more highly correlated with the shocks affecting the sectors they specialize in. We show how to decompose volatility into the various sources, quantify their contribution to aggregate volatility, and study how they relate to the stage of development. We document the following regularities. First, as countries develop, their productive structure moves from more volatile to less volatile sectors. Second, the volatility of country-specific macroeconomic shocks falls with development. Third, the covariance between sector-specific and country-specific shocks does not vary systematically with the level of development. There is also some evidence that the degree of sectoral concentration declines with development at early stages, and increases at later stages. We argue that many theories linking volatility and development are not consistent with these findings, and suggest new directions for future theoretical work.

Imports and Productivity

What is the effect of imports on productivity? To answer this question, we estimate a structural model of producers using product-level import data for a panel of Hungarian manufacturing firms from 1992 to 2001. In our model with heterogenous firms, producers choose to import or purchase domestically varieties of intermediate inputs. Imports affect firm productivity through expanding variety as well as improved input quality. The model leads to a production function where the total factor productivity of a firm depends on the share of inputs imported. To estimate this import-augmented production function, we extend the Olley and Pakes (1996) procedure for a setting with an additional state variable, the number of input varieties imported. Our results suggest that the role of imports is both statistically and economically significant. Imports are responsible for 30% of the growth in aggregate total factor productivity in Hungary during the 1990s. About 50% of this effect is through imports advancing firm level productivity, while the remaining 50% comes from the reallocation of capital and labour to importers.

Volatility and development

Why is GDP growth so much more volatile in poor countries than in rich ones? We identify four possible reasons: (i) poor countries specialize in more volatile sectors; (ii) poor countries specialize in fewer sectors; (iii) poor countries experience more frequent and more severe aggregate shocks (e.g. from macroeconomic policy); and (iv) poor countries' macroeconomic fluctuations are more highly correlated with the shocks of the sectors they specialize in. We show how to decompose volatility into these four sources, quantify their contribution to aggregate volatility, and study how they relate to the stage of development. We document the following regularities. First, as countries develop, their productive structure moves from more volatile to less volatile sectors. Second, the level of specialization declines with development at early stages, and slowly increases at later stages of development. Third, the volatility of country- specific macroeconomic shocks falls with development. Fourth, the covariance between sector-specific and country-specific shocks does not vary systematically with the level of development. We argue that many theories linking volatility and development are not consistent with these findings and suggest new directions for future theoretical work.

Halpern L, Koren M, G. A minimálbér költségvetési hatásai. In: Pritz P, Johancsik J, Baranyain頓zab, editors. A tudomány a gyakorlat szolgálatában: A foglalkoztatási szint bovítésének korlátai és lehetoségei. Budapest, Hungary: Magyar Tudományos Akadémia; 2004. p. 174-95.

Pricing to firm: an analysis of firm- and product-level import prices

We use Hungarian Customs data on product-level imports and exports of manufacturing firms to document that the import price of a particular product varies substantially across buying firms. Importantly, we can relate the level of import prices to firm characteristics such as size, foreign ownership and market power. We develop a theory of ‘pricing to firm’ (PTF), where markups depend on the technology and competitive environment of the buyer. The predictions of the model are confirmed by the data: import prices are higher for firms with greater market power, and for intermediate inputs with a high share in material costs. We take account of the endogeneity of the buyer's market power with respect to higher import prices. We show that even if unobserved cost heterogeneity within product categories is substantial, it is uncorrelated with our variables of interest. The magnitude of PTF is big: the standard deviation of price predicted by PTF is 21.5%.

Koren M. Buborékok a közgazdaságtanban. In: Csontos A, editor. Válogatás Maurice Obstfeld írásaiból. A Rajk László Szakkollégium által alapított Neumann János Díj 2003. évi kitüntetettjének tiszteletére. Budapest, Hungary: Aula; 2003. p. 51-2.
Koren M. Kockázatvállalás és nemzetközi diverzifikáció. In: Csontos A, editor. Válogatás Maurice Obstfeld írásaiból. A Rajk László Szakkollégium által alapított Neumann János Díj 2003. évi kitüntetettjének tiszteletére. Budapest, Hungary: Aula; 2003. p. 203-6.

Export pricing of foreign firms in Hungary : estimations for 1992-1996

We use Hungarian Customs data on product-level imports and exports of manufacturing firms to document that the import price of a particular product varies substantially across buying firms. Importantly, we can relate the level of import prices to firm characteristics such as size, foreign ownership and market power. We develop a theory of ‘pricing to firm’ (PTF), where markups depend on the technology and competitive environment of the buyer. The predictions of the model are confirmed by the data: import prices are higher for firms with greater market power, and for intermediate inputs with a high share in material costs. We take account of the endogeneity of the buyer's market power with respect to higher import prices. We show that even if unobserved cost heterogeneity within product categories is substantial, it is uncorrelated with our variables of interest. The magnitude of PTF is big: the standard deviation of price predicted by PTF is 21.5%.

Portfolio choice with illiquid assets

The present Paper investigates the effects of incorporating illiquidity in a standard dynamic portfolio choice problem. Lack of liquidity means that an asset cannot be immediately traded at any point in time. We find the portfolio share of financial wealth invested in illiquid assets given the liquidity premium. Benchmark calibrations imply a portfolio share of 2-6% in cash. These numbers are in line with survey data and also with portfolio recommendations by practitioners. We also find that long horizon investors invest more in illiquid assets. Overall, our results suggest that differences between asset classes unrelated to standard price risk may influence portfolio shares.