ESTIMATING MARK‐UPS FROM PLANT‐LEVEL DATA^*

Abstract

ResumoEste artigo investiga as conseqüências de ignorar a heterogeneidade dos preços na estimação de markups com uso de microdados. Demonstra-se que, ao ignorar tal heterogeneidade, as estimativas de markups são severamente tendenciosas em direção a um, independente do nível de competição. Para demonstrar tal resultado, constrói-se um modelo econométrico sob a hipótese de competição monopolística e uma função demanda CES, em um mercado de produtos diferenciados. Este modelo leva em conta a heterogeneidade não observada dos preços e mostra-se simples de estimar, dado que mesmo o método dos Mínimos Quadrados Ordinários é válido. Usando dados de fábricas Colombianas, o modelo de produtos diferenciados revela estimativas de markups consideravelmente acima da unidade, o que rejeita a hipótese de mercados em competição perfeita. AbstractThis paper investigates the consequences of ignoring price heterogeneity on the estimation of markups using micro-data. I show that ignoring output price heterogeneity yields markup estimates severely biased towards one regardless of competitiveness levels. To do so, I set up an econometric model that assumes monopolistic competition and a CES demand function in a differentiated product market. This model controls for unobserved price heterogeneity and is easy to estimate since OLS is applicable. Using data from Colombian plants, the differentiated product model reveals markup estimates considerably higher than one, rejecting the hypothesis of competitive markets.

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