Microfinance institutions (MFIs) provide a public good; if MFIs create and deepen markets where none existed before, there may be a case for public support. This book is based on a study of 45 MFIs, and applies factor analysis and cluster analysis to show that MFIs form clusters in terms of social and financial performance.PART I: INTRODUCTION Efficiency and Sustainability in Microfinance; B.Balkenhol PART II: CONCEPTUAL FRAMEWORK Poverty versus Inequality; A.Diop, I.Hillenkamp & J.M.Servet Poverty Reduction through Microfinance: A Capability Perspective; F.Comim Achieving Poverty Outreach, Impact and Sustainability: Managing Trade-Offs in Microfinance; A.Simanowitz Smart Subsidies; J.Morduch PART III: EMPIRICAL ANALYSIS Efficiency in Microfinance Institutions: An Application of Data Envelopment Analysis to MFIs in Peru; Y.Fl?ckiger & A.Vassiliev Efficiency in Financial Intermediation: Theory and Empirical Measurement; T.Beck Efficiency Drivers and Constraints: Empirical Findings; Y.Hamed Measuring the Performance of MFIs: An Application of Factor Analysis; G.F.Luzzi & S.Weber PART IV: SELECTED COUNTRY STUDIES Contextual Factors Determining Poverty Outreach and Financial Performance: The Case of Mali; R.Serra, F.Botti & M.Cherel-Robson Contextual Factors Determining Poverty Outreach and Financial Performance: The Case of Morocco; S.F.Meknassi Contextual Factors Determining Poverty Outreach and Financial Performance: The Case of Central and Eastern Europe; J.Pytkowska Auctioning Subsidies: Chile's 'Access to Credit Program'; V.S.Merino PART V: CONCLUSIONS Policy Implications; B.BalkenholTHORSTEN BECK World Bank, USAFABRIZIO BOTTI Cambridge University, UKMILASOA CHEREL-ROBSON Cambridge University, UKFLAVIO COMIM Cambridge University, UKAMADOU DIOP Institut Universitaire d'Etudes du Developpement, SwitzerlandYVES FL?CKIGER University of Geneva, SwitzerlandYOUSRA HAMED International Labour Office, SwitzerlandISABELLE HILLENKAMP Institut Universitaire d'ElãÉ