Until then, the Fed's policy committee, the Federal Open Market Committee (FOMC), did not have an explicit inflation target but regularly announced a desired target range for inflation (usually between 1.7% and 2%) measured by the personal consumption expenditures price index.

只能帮你找到维基的解释，一般都是规定好的，目前发达国家的目标通胀率都是2%。要计算都是计算当前一段时间的通货膨胀率