The bulk of what the world knows about the amounts and types of subsidies provided to specific sectors and sub-sectors comes mainly from intergovernmental organizations, such as the OECD.
The values of subsidies, or of support more widely, provided by OECD countries derive mostly from the OECD itself, or in the case of coal (until 2001) from the OECD's sister organization, the International Energy Agency (IEA). Estimates for the rest of the world come mainly from various one-off efforts by analysts working for the World Bank, the International Monetary Fund or one of the United Nations agencies, the IEA and from a few dedicated individuals.
As a result, when researchers combine the aggregate estimates from the sectoral accounts into global estimates of subsidies they are combining numbers based on different starting assumptions, different estimation methods, different policy coverage and even different time periods. Some normalization could be attained with a more careful approach to aggregation than some have used in past studies, although the level of comparability between these accounts is nowhere near that for corporate financial accounting.
