Common causes of slipping margins include increased product costs, increased shipping expense, finance costs, sales and discounting or inventory shrinkage due to theft or waste (food business).

FORBES: There Is Nothing Gross About Profit

The first data set, for the year 1999, came from 76 stores in a midsize retail chain and was used to weigh cash shortage and inventory shrinkage, the two most important sources of financial loss in retail, as a percentage of overall sales.

FORBES: Pay Employees More and They'll Steal Less

The cost is far outweighed by the savings in inventory, shrinkage and spoilage, which is why the simple everyday items that Taleb mentions are available to everybody today, not just aristocrats in the ancient times he so adores.

FORBES: Sorry Nassim Taleb, Technology Actually Does Matter