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Regular Addition of New Sample Enterprises to TANKAN

February 23, 2005
Bank of Japan
Research and Statistics Department

From the March 2005 TANKAN survey, 304 enterprises will be added to the sample of TANKAN (Short-term Economic Survey of Enterprises in Japan).

To prevent a decline in statistical accuracy due to a decrease in the number of sample enterprises caused by bankruptcies, mergers, and other factors, the statistical accuracy is examined once a year. When the examination reveals that statistical accuracy has in fact declined, new sample enterprises are added. (See "Sample Design and Sample Maintenance of TANKAN," June 7, 2004, Research and Statistics Department, Bank of Japan, for details.)

The statistical accuracy of the last TANKAN survey (December 2004) has recently been examined, and 304 enterprises will be added to the sample. As a result, the total number of the sample enterprises for the March 2005 TANKAN will be 10,650. The details are as follows:

(1) Sample Distribution

In TANKAN, population enterprises are classified into 377 strata, by industry and scale based on capital size and number of regular employees. Each stratum from which sample enterprises are extracted1 was examined for similarity between the distribution of the sample enterprises and that of the population enterprises.

The result revealed that there was no stratum in which the distribution of the sample had deviated from that of the population2. However, there were strata of which the sample distribution indicated a high likelihood of deviating from the distribution of the population with further decline in the number of sample enterprises.

To maintain statistical accuracy, 304 sample enterprises will be added to these strata (see the appendix for details).

  1. 40 strata with less than five population enterprises are excluded.
  2. The "test of the goodness of fit" using chi-square distribution is used in the regular examination. This method tests the null hypothesis, H0"The distribution of the sample and that of the population have the same shape." When the hypothesis is statistically rejected, it is judged that a deviation exists between the distribution of the sample enterprises and that of the population enterprises.

(2) Error Ratios of the Population Estimates

For all of the main six divisions by industry and scale (Manufacturing/Nonmanufacturing and Large/Medium-sized/Small, see below), the error ratios of the population estimates3 (measured by sales data), after the addition of 304 samples, remained within the target range.

  1. 3Population estimates based on sample surveys, like those in TANKAN, inevitably entail certain estimation errors. Users are advised to take this into consideration when using the data.

Error ratios (in sales) after the addition of 304 sample enterprises

For further information, please contact:

Business Survey
Research and Statistics Department
Bank of Japan

Email:post.rsd5@boj.or.jp


(Appendix)

Number of Sample Enterprises Added by Industry and Scale