The purpose of this coursebook is to establish inter-linkage among three different features of social wellbeing – namely equality, depolarization, and tax progressivity – all based on society's income distributions. Low equality is socially dispreferred since it refers to the accumulation of a highly significant part of the total income of the society in the possession of a few. Depolarization is concerned with the improvement in the level of wellbeing of the middle-income group of the society. The existence of a rich middle class in a society is always desirable, since a wealthy middle-income group contributes highly to the society's economic growth and development in many ways. Tax progressivity investigates the extent to which equality is raised through taxation.

Chapter 1 presents an introductory outline of the materials analyzed in the remaining chapters. Chapter 2 formally defines and analyzes the notion of equality. Chapter 3 provides a rigorous treatment of the concept of depolarization.

In Chapter 4 we discuss different structural or local indicators of tax progressivity that look at the extent of progression at each income point. We look particularly at the redistributive and departure from the proportionality effects of taxation. We also investigate the implication of structural measures with respect to depolarization. One section of the chapter examines the impacts of equal proportionate income growths on revenue and redistributive effects of taxation. Given the before-tax income distribution, the impacts of equal proportionate increase in taxes on structural measures are investigated as well.