The humble egg, one of nature’s perfect foods, a self-packaged, relatively inexpensive source of protein that can serve as a lowly hangover remedy or help a souffle rise to heavenly heights, is also a great teacher. It’s helping Americans understand how a free-market economy works: When demand is high and supply is low, prices rise.

The USDA said the combination of bird flu and inflation might drive up egg prices by another 20% this year. At Kuhns Market on the North Side, one of the first things we wanted to