"year-on-year" means the ratio of the same period, which generally refers to the comparison between the cumulative indicators of a certain month of this year and the cumulative indicators of the same month of the previous year. as the name suggests, "year-on-year decline" refers to the ratio between the cumulative indicator for this year and the cumulative indicator for the same month of the previous year.

calculation formula: ( ( b - a ) /b ) * 100