In 2018, the average OECD tax-to-GDP ratio remained virtually unchanged compared to 2017, with almost no increase (a change of 0.02 percentage points). This ends the trend of annual increases in the OECD average tax-to-GDP ratio observed since 2009, following the financial crisis. The slowing in the growth of the OECD average was predominantly driven by the impact of the significant fall in the tax-to-GDP ratio of the United States as a result of their tax reforms. However, due to rounding the OECD average tax-to-GDP ratio was 34.3% in 2018 compared to 34.2% in 2017.
In this publication, taxes are defined as compulsory, unrequited payments to general government. They are unrequited in that the benefits provided by governments to taxpayers are not normally allocated in proportion to their payments. Taxes are classified by their base: income, profits and capital gains; payroll; property; goods and services; and other taxes. Compulsory social security contributions (SSCs) paid to general government are also treated as taxes. Revenues are analysed by level of government: federal or central; state; local; and social security funds. Detailed information on the classifications applied is set out in the Interpretative Guide in Annex A.