物价指数是一个衡量市场上物价总水平变动情况的指数。物价总水平上升则意味着发生了通货膨胀，反之，物价总水平下降意味着通货紧缩，物价指数正是用来衡量经济中发生的通货膨胀或是通货紧缩的一个指标。如果物价指数上升过大则表明通货膨胀已成为了影响社会和经济不稳定的一个因素，央行就会有紧缩货币的政策和相关财政政策的颁布，对社会经济的发展有一定的影响。所以该指数的升高往往会对经济造成影响。物价指数是一种能够表示一个经济的宏观经济指标。

A price index (plural: “price indices” or “price indexes”) is a normalized average (typically a weighted average) of price relatives for a given class of goods or services in a given region, during a given interval of time. It is a statistic designed to help to compare how these price relatives, taken as a whole, differ between time periods or geographical locations.