Causal inference

Introduction

This part of the book provides an overview of causal inference with an emphasis on so-called quasi-experimental methods. This part of the book could be used as the core of a second semester-long course focused more on methods.

• 17  Natural experiments discusses the concept of the randomized controlled trial and the related idea of the natural experiment. While much discussed focuses on the value of random assignment for causal inference, we explain that other features of an experiment are also of critical importance. We explore the question of recognition versus disclosure to illustrate that the framing of the research question itself has important implications for any experiment.
• 18  Causal mechanisms covers ideas related to causal mechanisms. While this chapter is relatively less technical—there is no code at all in this chapter—we place this chapter here because it provides an important platform for thinking about issues in subsequent chapters.
• 19  Natural experiments revisited is a long, complex chapter covering a number of related ideas. Beginning with coverage of the so-called replication crisis in social sciences, we explore related issues using the setting of the much-studied Reg SHO experiment. Key ideas covered in this chapter include parallel trends and randomization inference.
• 20  Instrumental variables covers instrumental variable analysis with particular emphasis on reasoning about instruments.
• 21  Panel data covers panel data and fixed-effect regressions. The first part of the chapter returns to an example used in 3  Regression fundamentals before using a setting on voluntary disclosure to illustrate analytical choices related to the use of fixed effects.
• 22  Regression discontinuity designs provides an introduction to regression discontinuity designs.