Helpful chart! That’s what the authors concluded as well:
The first answer may be geographic: duck farming is concentrated in places that most Western animal advocacy organizations traditionally don’t pay attention to or don’t know as much about. The vast majority of the world’s duck production is concentrated in China and across Asia. Moreover, duck meat is relatively niche in the U.S., Canada, and much of Europe, aside from certain culinary subcultures or specific products like foie gras.
Helpful chart! That’s what the authors concluded as well: