The article presents a transversal analysis of the middle class. It makes references to the sources cited in the field. The middle class size is calculated based on the following indicators: wealth, income, consumption, occupation, level of training, middle class self-identification, values, leisure, etc. The middle class is studied by its global, regional, national, urban/ rural, gender, family, age characteristics, etc. Within the limits of this article, we aim to identify the middle class by region and country, and also by the basic indicators selected as personal wealth, income and consumption. Looking at how the middle class evolved globally over time, we will refer to the most relevant analyzes and sources cited internationally.