Tier 1 (93/232): Indicator is conceptually clear, has an internationally established methodology and standards are available, and data are regularly produced by countries for at least 50 per cent of countries and of the population in every region where the indicator is relevant. Tier 2 (66/232): Indicator is conceptually clear, has an internationally established methodology and standards are available, but data are not regularly produced by countries. Tier 3 (68/232): No internationally established methodology or standards are yet available for the indicator, but methodology/standards are being (or will be) developed or tested.