The price the government pays for standard weapons purchased from military contractors is determined by a pricing method called "historical costing" Historical costing allows contractors to protect their profits by adding a percentage increase, based on the current rate of inflation, to the previous year's contractual price.

Which of the following statements, if true, is the best basis for a criticism of historical costing as an economically sound pricing method for military contracts?

【选项】The rate of inflation has varied considerably over the past twenty years.