Is the pork weight artificially adjusted when compiling CPI？ Interpretation of National Bureau of Statistics

On October 18th, the State Council Office held a press conference on the national economy in the first three quarters of 2019. A reporter asked whether the National Bureau of Statistics adjusted the weight of pork when compiling cpi. In this regard, Mao Shengyong, director and spokesperson of the National Statistics Department of the National Bureau of Statistics, responded that the weights did change from month to month. The weight change is based on the proportion of goods and services in the total expenditure, and there is no artificial adjustment.

"I noticed that there have been some discussions on the Internet recently, whether the weight of pork has been adjusted. This is a more professional question. " Mao Shengyong said that the method used by the National Bureau of Statistics to calculate the price index is the chain Laplace calculation method, which is consistent with the international.

Specifically, how to calculate cpi? "We have to count the price changes of so many goods and services, but it is impossible to include all goods and services, so we should choose representative goods and services as the observation objects, which we call’ baskets’."

With the passage of time, goods and services will change. If they are representative in previous years, they will not be representative after two years, and the new ones will be included in this "basket", so we should choose a "base period". With the "base period" and the "basket", it is necessary to determine the weight of goods and services in the "basket".

How to determine the base period? The year of every 0 and every 5 is used as the base period of price statistics, which is also consistent with the international situation. For example, the current price statistics is based on 2015, and the representative goods and services should be selected according to the base period, which should be determined in strict accordance with the relevant data of household surveys. Once the goods and services and their quantities are determined, the basket is fixed. So it is called fixed base period and fixed basket.

After fixing the basket, it depends on the changes of the goods and services in the basket, and each kind of goods and services has weight. How to determine the weight? This is based on the proportion of consumption expenditure of this kind of goods and services in the total expenditure of the whole basket as the weight.

For example, Mao Shengyong said, for example, the cpi in September, the ring ratio, such as the weight of pork, is the proportion of pork consumption expenditure in the whole consumption expenditure in August as its weight; Calculate the year-on-year increase of pork in September, and use the proportion of pork consumption expenditure in the whole consumption expenditure in September last year as the weight. In this way, the base period of each month is fixed and the basket is fixed, but the weight is changed.

"The weight change is based on the proportion of the expenditure of such goods and services in the total expenditure, and there is no artificial adjustment. The weight does change from month to month, and there are still scholars in the society who pay attention to this issue. " Mao Shengyong said.

In addition, the changes in consumer prices basically reflect the characteristics and trends of price changes. "We say that statistical data is more macro data, a comprehensive indicator, a comprehensive and average reflection of all economies and all economic activities in the whole society, and reflects the overall situation." Mao Shengyong said that there are inevitably different groups, different individual feelings and inconsistent overall data. Sometimes, if we simply use structural data or individual data to infer the overall situation, there will be some deviations.

According to the data released by the National Bureau of Statistics on October 15th, cpi rose by 3.0% year-on-year in September, an increase of 0.2 percentage points over the previous month. Mao Shengyong said that in the cpi of 3%, although the price of pork is relatively high, the weight of pork or pork consumption accounts for only a little more than 2% of the total consumption expenditure, and there are more than 90% industrial consumer goods, other foods and services, and their prices have risen slightly, some have fallen, and some have risen moderately. After weighted average, they have gained a 3% increase, which reflects the basic characteristics of current price changes.

Editor-in-Chief: Qin Hong

Author: The Paper

Text Editor: Li Linwei

Source: Xinhua News Agency

Photo editor: Cao Liyuan