Santos, Jorge M. A.Negas, Elsa RosárioCavique, Luís2014-01-142014-01-142013978-94-007-5738-7 (Print)978-94-007-5739-4 (Online)http://hdl.handle.net/10400.2/2799This chapter introduces the basics of data envelopment analysis techniques, with a short historical introduction and examples of the constant returns to scale model (CRS) and the variable returns to scale (VRS) model. The ratio models are linearized and for both orientations primal and dual models are presented.engData envelopment analysisEfficiency evaluationbook part