Spanish Abstract: ? Las Empresas Publicas funcionan en general con una menor eficiencia que sus equivalentes Privadas, como reza el topico al respecto? Se trata de un lugar comun utilizado profusamente como un axioma indiscutible, principalmente desde posiciones politicas conservadoras. Aunque tambien frecuentemente asumido por publicaciones, comentaristas o politicos que no pretenden serlo. A este topico contribuye, sin duda, que desde la teoria economica dominante, la especifica ‘teoria de los derechos de propiedad’ sostiene en su tesis principal la prediccion de que en el caso de una empresa publica la persona que la gestione (Director/a General, o el equipo directivo) sera necesariamente menos eficaz que en caso de una empresa privada principalmente porque el sistema de control e incentivos sobre su gestion (por parte de la instancia publica propietaria) sera a su vez o inexistente o muy poco eficaz.Independientemente de que las premisas en que se basa tal teoria pueda estimarse que no se dan en muchos casos, ?Que nos muestra la observacion de la realidad? ?Que nos dice la evidencia empirica sobre tal lugar comun respecto a si las empresas publicas son en general o ‘por naturaleza’ menos eficientes?El objetivo del presente trabajo es presentar y analizar la evidencia empirica acumulada durante decadas al respecto a escala internacional (apartados 2 y 3). Es decir, estudios empiricos que tratan de comparar, utilizando ciertos indicadores, la eficiencia de empresas publicas (EP) con la de empresas privadas (PR). Se trata en cualquier caso de investigaciones publicadas en revistas academicas reconocidas internacionalmente, o en publicaciones equivalentes de instituciones economicas como el Banco Mundial, el Banco de Espana, etc.Puede anticiparse que entre las conclusiones generales aqui derivadas del analisis de ese conjunto de estudios empiricos (alrededor de 160) –y expuestas en el apartado 4- destaca la de que en una parte mayoritaria de esos estudios –entre 2/3 y un 58%- sus autores concluyeron que las empresas privadas de la muestra examinada presentaban un mayor nivel de eficiencia -segun el indicador utilizado- que en el caso de las empresas publicas incluidas en la muestra. Y que en el resto de los estudios recopilados –entre 1/3 y un 42% de ellos- los autores concluyeron que no detectaron diferencias significativas, o bien que las empresas publicas de la muestra presentaban mejores niveles para los indicadores de eficiencia que los de las privadas con las que se comparaban.Esto permite afirmar pues que la referida prediccion de la teoria de los derechos de propiedad -sobre que siempre o en general o por naturaleza las empresas publicas seran menos eficientes- no se cumple en la realidad en un numero significativo de casos: entre 1/3 y un 42%; (por lo que cabe suponer que tal teoria debe estar desde hace tiempo en curso de ser reformulada en las agendas de los correspondientes teoricos).Por otra parte, un analisis mas detallado de los 160 estudios referidos -considerando solo aquellos en que consta explicitamente que el indicador de eficiencia utilizado para basar las conclusiones no era tipo beneficios (dado sus limitaciones en cuanto a medir la eficiencia, discutidas aqui)- permite anadir que la proporcion anterior (2/3 - 1/3) pasa al 50-50%: Es decir, igual numero de estudios que concluyen que las empresas publicas estudiadas fueron menos eficientes como de estudios que concluyen que no.El presente informe finaliza con un resumen del ‘estado de la cuestion’ segun lo anterior (punto 5.1), asi como con un intento de contestar unas peguntas relevantes que tal estado de la cuestion sugieren (punto 5.2): ?De que depende que una determinada empresa que, como la EP, no es gestionada por sus propietarios (situacion que de hecho es la dominante tambien en medianas y grandes empresas privadas) sea mas o menos eficiente? ?Cuales son las condiciones que hacen que esa empresa –sea publica o privada- pueda mejorar su eficiencia? O, visto desde otra perspectiva ?Cuales son los ‘defectos’ que explicarian una menor eficiencia comparativa -y cuya eliminacion permitirian que la empresa en cuestion mejorase su eficiencia?Disculpas anticipadas al/a lector/a si encuentra que la respuesta que encontrara al final para tales preguntas no es corta y perfectamente definida sino un tanto compleja.English Abstract: Do the Public Owned Enterprises operate generally with a lower efficiency than their Private equivalents, as the topical on the matter goes? It is certainly a common place, profusely used as an unquestionable axiom, mainly from conservative political positions. Although frequently also assumed by publications, commentators or politicians that do not consider themselves to be so. Of course, It contributes to that topical statement the fact that from the dominant economic theory, the specific one “theory of the property rights” supports in its main thesis the prediction that in the case of a public owned company the person who manages it (President, CEO, or the top-managers team) will be necessarily less effective than in case of a private enterprise; mainly because the control-and-incentive system – which will be applied by the public-property representatives (Administration) – in order to assess and motivate the company’s management will be either nonexistent or very little effective.Independent of the fact that the premises on which is based such prediction can be considered that they do not hold in many cases, What in the end the observation of reality shows to us about? What says to us the empirical evidence on such a common place – regarding if the public owned enterprises (PE) are generally or “by nature” less efficient than the private ones (PR)? The objective of this work is to present and analyze the empirical evidence on the matter that has been accumulated at international scale along last decades (sections 2 and 3): I.e., those empirical studies that try to compare, using certain indicators, the efficiency level of PE with the one of PR. Which means comparative research published in academic internationally-recognized journals, or equivalent publications by economic institutions like the World Bank, the Bank of Spain, etc.It can be anticipated that, among the general conclusions derived here (set out in section 4) from the analysis of the set of available empirical studies (around 160), it highlights the following one: In most of those studies – between 2/3 and 58% of them – their authors concluded that PR enterprises of the samples under analysis presented an efficiency-indicator level better than in the case of the PE in the sample. And that in the remaining compiled studies – between 1/3 and 42% – the authors conclude that they either did not detect significant differences or that the PE in the respective sample presented better indicators of efficiency than the PR they were compared with.This therefore allows to say that the referred prediction of the ‘theory of the property rights’ regarding PE always or in generally or by nature will perform as less efficient, is not fulfilled in the reality for a significant number of cases; (hence, it can be assumed that such theory must be since time ago on the way of being reformulated – as a task in the agendas of the corresponding theoreticians).On the other hand, a more detailed analysis of the referred 160 studies – by considering just those in which it is sure that the efficiency indicator used for drawing the conclusions was not benefits-type (because its limitations for efficiency measures, here discussed), allows to add that the above proportion (2/3-1/3) happens to change to 50-50%: That is, the same number of studies concluding that PE companies were less efficient, that studies concluding they do not.The present report finalizes with a summary on the “state of the question” according to the evidence presented and discussed (point 5,1), as well with an attempt to answer some relevant questions aroused by such state of the art (point 5,2). Thus: What it makes that a certain company, like a PE, which is not managed by its proprietors (a situation which is in fact dominant also among middle and large private enterprises), be more or less efficient? Which are the conditions that make that company – be it public or private – may improve its efficiency? Or, from another perspective, which are the shortcomings that would explain a lower comparative efficiency (and whose elimination would allow the referred company to improve its efficiency)?Apologies in advance to the reader if s/he feels that the answers to such questions that s/he will find at the end are not short and clear-cut but somewhat complex.