Gareth: Baked into the analysis of the supply side constraints to rising prices are government regulatory policy. You do well to point out the trade related policies impacting chicken prices as another example being driven largely by trade policy through raising tariffs.
Following the Mises SA article you refer to (published in March 2012), wherein Colin Phillips predicted chicken prices will rise owing to government trade policy, note that Woolworths pre-cooked quarter chicken piece prices have increased 18% from July 2012 to January 2013. That’s an increase of nearly 40% annualised! The proof is below. Click to enlarge.