The EF English Proficiency Index (EF EPI) attempts to rank countries by the equity of English language skills amongst those adults who took the EF test. It is the product of EF Education First, an international education company, and draws its conclusions from data collected via English tests available for free over the internet. The index is an online survey first published in 2011based on test data from 1.7 million test takers. The most recent edition was released in November 2023.

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So the data is not representative for the entire population of a country.