Ring comparison is the comparison between the current statistical cycle and the previous statistical cycle. For example, comparing July 2005 with June 2005 is called ring comparison.

The development speed of the chain is the ratio of the level of the reporting period to the level of the previous period, indicating the development speed of the phenomenon in different periods. If the comparison between each month of a year and last month is calculated, that is, February is 1 month, March is 1 month, and April is 1 month, indicating the development degree of each month. For example, we analyze the development trend of some economic phenomena during the fight against SARS, and the ring ratio is more telling than the same period last year.

There are two methods of ring comparison: ring comparison growth rate and ring comparison development rate.

Compared with the previous period.

Chain growth rate = (current period-previous period)/previous period * 100%

Reflect how much this period has increased compared with the previous period.

Serial development speed = current period/previous period * 100%

Reflect how much this period has increased compared with the previous period.

For example, the current sales volume is 5 million, and the previous sales volume was 3.5 million.

Chain growth rate = (500-350)/350 *100% = 42.86%

Chain development speed = 500/350 *100% =142.86%