As noted above, the exclusion of the 16 as an "official" skeet gauge certainly hurt. So did the advent of the 3" 20ga. So did American manufacturers cutting corners and building 16's on 12ga frames. I think it will retain popularity especially among sxs shooters. We're clearly a niche market anyhow. But a properly proportioned 16 is an excellent upland gun.
Larry;
I think that is a pretty good summation of the falling popularity of the 16. Trap shooting was always primarily a 12 gauge game. The 16 was more popular in the uplands for many years. Those who shot Skeet as well as hunted naturally turned to the 20 for an upland gun for they were most likely set up to load for it. After Skeet was introduced the 20 gradually gained in popularity then with the introduction of the 3" chambering it gained even more. I am fastly approaching 79 years of age & can well remember when one saw more Southern "Bird Hunters" (Quail) carrying far more 16's than 20's & this applied to pumps & the Hump-Back Browning as well. The Browning Sweet 16 was a very popular gun among Bird Hunters.
In my part of the South at least one might go Turkey hunting, Dove Shooting, Duck or Goose Hunting etc, but nobody went Quail Hunting, they went Bird Hunting.