This is from Timmothy Taylor, the Conversable Economist: (Hat tip to Dr. John Goodman)
On the demand side, the quantity of turkey per person consumed rose dramatically from the mid-1970s up to about 1990, but since then has declined somewhat. The figure below is from the Eatturkey.com website run by the National Turkey Federation. Apparently, the Classic Thanksgiving Dinner is becoming slightly less widespread.
