"This thesis is composed of 3 papers. The first paper proposes a theoretical model for informality in the labour markets of developing countries which reflects the latest developments in empirical research and aims at using a structural estimation to estimate the impacts of labour market interventions in developing countries. The second paper proposes carrying out a quasi-experimental evaluation of an Active Labour Market Program in Pakistan with a particular focus on the informal sector and its importance for the participants participating in the program. The third paper explores the rise of the "gig" economy as a new form of informality in advanced economies."