immediately adopt the necessary measures to prevent, diminish and eliminate the conditions and attitudes which cause or perpetuate substantive or de facto discrimination. For example, ensuring that all individuals have equal access to adequate housing, water and sanitation will help to overcome discrimination against women and girl children and persons living in informal settlements and rural areas. Discrimination may also be categorized as direct or indirect. Direct discrimination occurs when an individual is treated less favourably than another person in a similar situation for a reason related to a prohibited ground.77 By contrast, indirect discrimination refers to cases of de facto discrimination, where a law, policy or practice may appear neutral on its face, but nonetheless has a disproportionate impact on the exercise of ICESCR rights “as distinguished by prohibited grounds of discrimination.”78 Prohibited grounds Article 2(2) provides an illustrative list of prohibited grounds of discrimination under ICESCR. These grounds are race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status.79 This list is not exhaustive, however; the expression “other status” in Article 2(2) paves the way for arguments in favour of adding further grounds of discrimination. To this end, the CESCR has identified the following grounds of non-discrimination in addition to those listed explicitly in Article 2(2): disability, age, nationality, marital and family status, sexual orientation and gender identity, health status, place of residence, and economic and social situation.80 Other provisions of the ICESCR reiterate certain applications of the prohibition of discrimination in the enjoyment of economic, social and cultural rights, further highlighting the prohibition of discrimination between men and women (Art. 3); in the workplace (Art. 7(a)(i) and (c)); and in access to higher education (Art. 13(2)(c)). Permissible Scope of Differential Treatment Although prohibited in principle, differential treatment based on “grounds of discrimination” may nonetheless be justified (and, therefore, permitted) under exceptional circumstances. According to the CESCR, such justification requires that the differential treatment be “legitimate, compatible with the nature of the Covenant rights and solely for the purpose of promoting the general welfare in a democratic society.”81 In addition, the justification of such differential treatment requires a “clear and reasonable relationship of proportionality between the aim sought to be realized and the measures or omissions and their effects.”82 Thus, a justified differentiation based on a prohibited ground is allowed if it is lawful (not arbitrary), based on objective elements, and reasonable in its consequences. 28