"Even when bonuses and incentives were effective in changing behavior, they often created other problems. Central planning was just not good at replacing what the great eighteenth-century economist Adam Smith called the "invisible hand" of the market. When the plan was formulated in tons of steel sheet, the sheet was made too heavy. When it was formulated in terms of area of steel sheet, the sheet was made too thin. When the plan for chandeliers was made in tons, they were so heavy, they could hardly hang from ceilings."