Hey #medlibs out there. I have a dumb PubMed question on term explosion with subheadings: In the 4 queries on the first pic (see ALT-Text for a copyable version) the numbers for the exploded codeine search are much higher than the combined numbers of the other three.
The behavior is different if I don't work with subheadings (cf. second pic). Then the numbers of the non-exploded main term and two more specific terms add up to a little more than the exploded main term. This makes sense as I would expect some papers to be on both levels of the hierarchy.
Anybody out there got an explanation for the behavior in the first picture.