【中文版】

CPI是指消费者物价指数，是反映一定时期内城乡居民所购买的生活消费品和服务项目价格变动趋势和程度的相对数。CPI是度量消费商品及服务项目价格水平随着时间变动的相对数，反映的是通货膨胀或紧缩的程度。

CPI通常是以百分数的形式表示，以2010年为基期，100为基数。如果某期的CPI大于100，则表示该期的价格水平比基期上升了；如果某期的CPI小于100，则表示该期的价格水平比基期下降了。

CPI是一个非常重要的经济指标，它不仅影响居民的消费行为，还影响政府的财政政策和货币政策的制定。如果CPI持续上升，则可能表明通货膨胀的压力正在增加，中央银行可能会采取紧缩的货币政策来控制通货膨胀。相反，如果CPI持续下降，则可能表明市场需求不足，经济可能正在萎缩，中央银行可能会采取宽松的货币政策来刺激经济增长。

此外，CPI还被用于计算国内生产总值平减指数，这是一个用于衡量经济总体价格水平的指数。

总的来说，CPI是衡量通货膨胀或紧缩的重要指标，对于宏观经济政策的制定和实施具有重要意义。

【英文版】

CPI, which stands for Consumer Price Index, is a relative number reflecting the price trend and degree of consumer goods and service items purchased by urban and rural residents in a certain period of time. CPI is a measure of the change in the price level of consumer goods and service items over time, reflecting the degree of inflation or deflation.

CPI is usually expressed in percentage form, with 2010 as the base period and 100 as the base. If the CPI for a certain period is greater than 100, it means that the price level for that period has increased compared to the base period; if the CPI for a certain period is less than 100, it means that the price level for that period has decreased compared to the base period.

CPI is a very important economic indicator that affects not only consumers' consumption behavior but also the government's fiscal policy and monetary policy formulation. If the CPI continues to rise, it may indicate that inflationary pressure is increasing, and the central bank may adopt tight monetary policy to control inflation.相反，如果CPI持续下降，则可能表明 market demand is insufficient, the economy may be shrinking, and the central bank may adopt loose monetary policy to stimulate economic growth.

In addition, CPI is also used to calculate the GDP deflator, which is an index used to measure the overall price level of the economy.

Overall, CPI is an important indicator for measuring inflation or deflation, and it has great significance for the formulation and implementation of macroeconomic policies.