In reply to Rick Anderson.

Oh good point. I'll fix that. That said I stand by my point that the disagreement lies in how you define "market power". Authors can both have choice and have zero market power (or if you prefer have market power but not an effect on price).

I agree with you that authors do have market power but that we have conditions where that could lead to a run away luxury goods market, leading to a rise in prices, on which I agree with Schulenberger (and disagree with the me of a few years back as well to be fair!).

In either case you point up a lack of clarity in the prose which I'll look to improve on in, either here or in future versions at least.