As the Convention stipulates, the OECD is not an organisation just for members. It aims to contribute to the sound economic development of both member and non-member countries. Nevertheless, the global share of the OECD has been continuously dwindling. In 2030, the share of OECD member countries of the global economy is expected to decrease to 43%. This means that, in order to enhance its relevance, the OECD continues to strengthen its engagement with and outreach to non-member countries.
The OECD has been expanding its membership continuously. Especially around the mid-1990s, when Korea joined the OECD, Mexico and some Eastern European transition countries joined. In 2010, four countries ; Chile, Estonia, Israel, and Slovenia acceded to the OECD, increasing the number of members to 34. After Latvia in 2016, Lithuania in 2018, Colombia joined in 2020, Costa Rica joined in 2021, bringing the total to 38.
Aside from the expansion of its number of members, the OECD has recently been using various external-relations tool such as Key Partner programs, country programs, and regional programs to enhance its global influence. To engage further with big players such as Brazil, China, India, Indonesia, and South Africa, in 2007 the OECD started Enhanced Engagement programs, whose name was later changed to Key Partners. With these different programs, the OECD currently works in some capacity with over 120 governments and jurisdictions across the globe.
In addition to working with governments, the OECD has close working relationships with other international organisations such as the IMF, the WB, and the World Trade Organisation (WTO), and it contributes substantially to the G7 and G20. It also collaborates with major regional banks, as well as many other international banks and organisations. Increasingly, the OECD works with a wide range of policy shapers that go beyond governments, including a network of parliamentarians and legislators, business and a labor-advisory bodies (the Business Industry Advisory Committee, BIAC, and the Trade Union Advisory Committee, TUAC), and partnerships with numerous civil-society organisations.
The OECD has more than 20 Part II programs, in which some or all members or non-members may participate. Under the larger name of the OECD family, some Part II organisations have a very strong independency. The International Transport Forum (ITF), Financial Action Task Force (FATF), and Sahel and West Africa Club (SWAC) are not OECD bodies, though the OECD might have some fiduciary duties as they share the OECD Secretariat. In case of the International Energy Agency (IEA), the Nuclear Energy Agency (NEA), and the Development Center (DEV), they are referred as autonomous organisations, although they were established within the framework of OECD. The level of independence of these organisation varies. The IEA is more independently operated than, for example, the NEA, DEV, or the Global Forum on Tax Transparency and Exchange of Information for Tax Purposes (GFTEI).
source : OECD, https://www.oecd.org/general/organisationforeuropeaneconomicco-operation.htm