I'm not an academic researcher so I don't have the raw data that you want, but I think it's worth not missing the forest for the trees.

Bee populations have been demonstrably stressed for a very long time, and CCD and other more recent developments are yet another sign.

The need for beekeepers to aggressively split hives is a sign that things are going very badly for them, even if we manage to raise the number of colonies in the short term.

Note that there are plenty of other parts of our ecosystem that show signs of severe stress as well (e.g. amphibians, coral reefs, etc.); we may very well reach a tipping point where large swaths of various food chains catastrophically collapse.