As the research is limited on the determinants of individual social situation, a bad objective specification of the inequality concept could not create many problems. However, the efforts furnished for testing hypothesis to explain why the economic inequality is greater in some societies rather than others, how it varies from one area to another, have led researchers to tackle this question from statistical point of view. Many indicators (Jackman, 1974; Kelley&Klein, 1977; Morris C, 1972; etc..) are constructed to understand better this socio-economic concept. With the proliferation of inequality measures, the question of relevance arises naturally. Which indicator one must choose in order to compare different socio-economic realities? In the absence of criteria to make a choice, users are generally guided by convenience or familiarity. Note also that, if the sociological notion of inequality seems elusive, its contours can be identified fairly well economically. Thus, one can find in this field enough material to understand the characteristics of that concept. The aim here is to characterize inequality indicators. We begin by assessing theses ones in terms of properties and characteristics that underpin the concept. This allows to study the relevance of certain indicators frequently used, and to appreciate the methodological and theoretical implications of these measures.