This working paper summarises the main findings of a data collection exercise documenting the size of the national state-owned enterprise (SOE) sectors in OECD countries (in terms of number, employment and economic value of enterprises), and provides a breakdown by main sectors and types of incorporation. The data is based on questionnaire responses from national governments, covering the years 2008 and 2009. Twenty-seven of the Organisation.s 34 member countries have contributed to date. Employment in SOEs across the OECD area exceeds 6 million people, and that the value of all SOEs combined is close to US$ 2 trillion. In addition to this, the State in many countries holds minority stakes in listed enterprises that are large enough to confer effective control. These enterprises employ a further 3 million people and are valued at close to US$ 1 trillion. Hence, while state ownership of enterprises has declined in recent decades, SOEs and similar entities continue to account for a significant part of the corporate economy in many countries. Following decades of privatisation, the remaining SOEs have a strong sectoral concentration. Around half (in value terms) of all SOEs in OECD countries are located in the network sectors, mostly transportation, power generation and other energy. A further fourth of total valuation is accounted for by financial institutions. In addition, among the partly state-owned listed companies there are many partly privatised telecommunications companies. In other words, not only do state-invested enterprises remain significant, they are also increasingly concentrated in a few ¡°strategic¡± sectors of great importance to the competitiveness of the rest of the business sector.