• 1 Introduction
  • 2 Parametric metrics
  • 2.1 Linear models
  • 2.2 Nonlinear models
  • 3 Non- and semiparametric models
  • 3.1 Pooled models
  • 3.2 Random effects models
  • 3.3 Fixed effects model
  • 3.4 Models with sample attrition
  • 4 Concluding remarks
  • References