ResumenEn un contexto de libre entrada analizamos los cambios que se producen en el excedente del consumidor y en el bienestar social, así como en las demás condiciones del equilibrio, cuando entra un competidor en un mercado monopolístico en el que existe una firma establecida. Abordamos el equilibrio en un modelo de duopolio asumiendo que el entrante sigue un único periodo de competencia en cantidades Cournot-Nash. Incorporamos los costos de retención al modelo de Klemperer (1988). El entrante, con el fin de atraer a un cliente, asume los costos de cambio de proveedor en que incurre el consumidor; la firma establecida asume los costos de retención para conservarlo. Suponemos una demanda lineal y costos marginales de ambas firmas constantes. Los resultados del trabajo son importantes para el análisis de las implicaciones sobre bienestar social de las políticas regulatorias. Realizamos una simulación del modelo teórico y confirmamos los resultados relevantes en términos de bienestar social, excedente del consumidor, beneficios y cantidades en monopolio y en duopolio con costos de cambio y con costos de cambio y de retención. Palabras clave: políticas públicas de apertura; costos de cambio; costos de retención; excedente del consumidor; bienestar social.

The empirical analysis of the impact of market potential on the spatial distribution of human capital has often taken the approach of using samples of large economic areas (world sample of countries, Europe, single countries). This paper proposes to strengthen the analysis of +the potential "fractal dimension" of the market potentialhuman capital relation by estimating econometric specifications which relate educational attainment levels to market potential for the 53 Galician counties using yearly data over the period 2005-2012 and census data for 2001 and 2011. We find evidence that market potential exerts a positive impact on the spatial distribution of human capital across the Galician counties, concluding therefore in favour of the fractal dimension. These results could also help to explain the (lack of) convergence in terms of income between the Western and Eastern parts of Galicia.

This article examines the costs of switching that may exist in the European postal sector, where it is carried out an ambitious process of opening to competition since 1997. Inadequate regulation of the access to some elements of postal infrastructure or services within the scope of the universal postal service exists. This article proposes adaptations to ensure transparent and non-discriminatory access conditions to elements of postal infrastructure in line with the sectorial directives aimed at strengthening competition in the long term in the postal market. The proposed adaptations focus on services such as postcode systems, address databases, post office boxes, delivery boxes, re-direction and return to sender services. All of them can help reduce the switching cost and thus strengthen competition.