We now have the makings of a great social experiment (provided that Cadbury makes no changes, in the meantime). If we can ascribe any shifting in market share to Hershey’s changes; then we (and corporate boards, and lawmakers) will know the dollar cost of such changes.
Cadbury already has made changes. There was a thread before Easter about smaller eggs.
This, http://www.bravotv.com/blogs/are-favorite-easter-candies-like-cadbury-creme-eggs-shrinking , talks about how a few years ago, they went from 6 to a box to 5 for the same price. Today, there are 4 to a box and have lost 6 grams in weight each.