Various mean values are given in the OECD statistics. These take into account the OECD countries for which data are available or can be estimated. The value for the "OECD average" is calculated as the unweighted mean of the data values for all OECD countries. "Total OECD" is calculated as the weighted mean of the data values of all OECD countries. The "EU average" is calculated as the unweighted mean of the data values of the OECD countries that are members of the European Union. The United Kingdom's exit from the European Union on 31 January 2020 will be taken into account as an EU22 average (formerly "EU19, EU21, EU22 or EU23 average"). For more information on which countries were included in the calculation of the international averages in the individual reporting years, see source.
(Source: OECD, Education at a Glance)