The OECD has published the Handbook on Internationally Comparative Educational Statistics. It was constructed on the basis of input from various national governments, experts of the OECD´s Indicators of Education Systems programme (INES) and the OECD’s Innovation and Measuring Progress Division (IMEP). It provides the definitions and conventions used in the underlying data collections as well as the methodologies used to compile the published statistics and indicators derived from them.
It contains a special paragraph on the challenges in measuring student mobility, such as distance learning, cross-border commuting students, mobility without registration at the host, off-shore campuses and International and European schools. It offers definitions of internationally mobile vs foreign and exchange students, but also still identifies the need for better mobility data collection.
This is not rocket science: if those involved in statistical data in education heed to and comply with the comparability recommendations of this handbook, the ensuing statistical analyses will become internationally comparable. If the handbook is not heeded, statistical data on international mobility and other indicators for internationalisation must still be used with care.