E/C.12/GC/20 page 5 Systemic discrimination 12. The Committee has regularly found that discrimination against some groups is pervasive and persistent and deeply entrenched in social behaviour and organization, often involving unchallenged or indirect discrimination. Such systemic discrimination can be understood as legal rules, policies, practices or predominant cultural attitudes in either the public or private sector which create relative disadvantages for some groups, and privileges for other groups. Permissible scope of differential treatment 13. Differential treatment based on prohibited grounds will be viewed as discriminatory unless the justification for differentiation is reasonable and objective. This will include an assessment as to whether the aim and effects of the measures or omissions are legitimate, compatible with the nature of the Covenant rights and solely for the purpose of promoting the general welfare in a democratic society. In addition, there must be a clear and reasonable relationship of proportionality between the aim sought to be realized and the measures or omissions and their effects. A failure to remove differential treatment on the basis of a lack of available resources is not an objective and reasonable justification unless every effort has been made to use all resources that are at the State party’s disposition in an effort to address and eliminate the discrimination, as a matter of priority. 14. Under international law, a failure to act in good faith to comply with the obligation in article 2, paragraph 2, to guarantee that the rights enunciated in the Covenant will be exercised without discrimination amounts to a violation. Covenant rights can be violated through the direct action or omission by States parties, including through their institutions or agencies at the national and local levels. States parties should also ensure that they refrain from discriminatory practices in international cooperation and assistance and take steps to ensure that all actors under their jurisdiction do likewise. III. PROHIBITED GROUNDS OF DISCRIMINATION 15. Article 2, paragraph 2, lists the prohibited grounds of discrimination as “race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status”. The inclusion of “other status” indicates that this list is not exhaustive and other grounds may be incorporated in this category. The express grounds and a number of implied grounds under “other status” are discussed below. The examples of differential treatment presented in this section are merely illustrative and they are not intended to represent the full scope of possible discriminatory treatment under the relevant prohibited ground, nor a conclusive finding that such differential treatment will amount to discrimination in every situation. Membership of a group 16. In determining whether a person is distinguished by one or more of the prohibited grounds, identification shall, if no justification exists to the contrary, be based upon self-identification by the individual concerned. Membership also includes association with a group characterized by one of the prohibited grounds (e.g. the parent of a child with a disability) or perception by others that an individual is part of such a group (e.g. a person has a similar skin colour or is a supporter of the rights of a particular group or a past member of a group).