In part, low coverage reflects the high incidence of informality and self-employment. While workers in informal employment cannot be affiliated to social security, it is not always compulsory for the self-employed, and when it is, it tends to be difficult to enforce. The share of self-employed in total employment is around 40% in Indonesia and between 20 and 30% in most of the other emerging economies, well above the average OECD share of about 15% (see Annex 2.A2 in OECD, 2011b for details). Moreover, coverage of contributory programmes is concentrated among better-off workers.