A vulnerability approach to the definition of the middle class

Measurement of the middle class has recently come to the center of policy debate in middle-income countries as they search for the potential engines of growth and good governance. This debate assumes, first, that there is a meaningful definition of class, and second, that the thresholds which define relatively homogeneous groups in terms of pre-determined sociological characteristics can be found empirically. This paper aims at proposing a view of the middle class based on vulnerability to poverty. Following this approach the paper exploits panel data to determine the amount of comparable income -associated with a low probability of falling into poverty- which could define the lower bound of the middle class. It looks at absolute thresholds, challenging the view that people just above the poverty line are actually part of the middle class. In an analogy with poverty measurement, there is a degree of arbitrariness in the definition of specific thresholds, but the concept behind them is clear and economically meaningful. The estimated lower-threshold is used in cross-section surveys to quantify the size and the evolution of middle classes in Chile, Mexico, and Peru over the past two decades. The evidence also shows that the middle class has increased significantly in all three countries. There is an important group of people, however, who cannot be defined as middle class from this perspective, but remain vulnerable to fall back into poverty.