What does a country average actually mean?

Dirk van Damme:

The international statistical system, one of the great achievements of international organisations, has mirrored the evolution of the nation-state. International statistics – and those related to education are no exception – were tuned towards comparing and benchmarking countries against each other. National averages thus became the dominant data. Most of the data points in Education at a Glance, for example, are national averages. However, the expansion and increased sophistication of data collection and data processing have allowed for the development of many more measures than just national averages. Indeed, averages without m