This research does not measure everything. Two large areas left out are how much the textbook goes into empirical evidence, and its didactic qualities.

• How much empirical evidence is discussed

This would often amount to measuring how extensive and detailed a textbook is as longer textbooks are more likely to devote more text to discussing empirical evidence. Rather than favouring long textbooks, we therefore decide to judge the textbooks solely based on whether the presentation of the topic is in agreement or contradicts empirical findings, not whether it discusses those empirical findings. Of course, it is highly relevant to observe whether textbooks do discuss the empirical findings themselves. We encourage experts to include this in the texts about the good and bad practices. But we do not include it in the scoring.

• Didactic quality of the explanations of the topic

This is highly relevant for which textbook is most effective at teaching students economics. We have, however, decided to limit the scope of this study to the content itself, rather than the didactic quality of its presentation. An assessment of didactic quality requires different expertise and measurement methods. The didactic aspect of economics education receives substantially more attention in research than its content does. To maximise our added benefit we therefore focus on the less often studied aspect of the content.