Year On Year, particularly in the context of percentage growth or decline.
The year-on-year change is calculated from successive years' data as:
YOY change = ( Later year / Earlier year ) - 1
Later year and Earlier year = two years, exactly one year apart
Revenues have grown as follows:
Year 1: $100m
Year 2: $110m
Year 3: $132m
The related year-on-year (YOY) percentage growth figures are:
110/100 - 1
Also known as Y/Y.
YOY is different from the compound annual growth rate (CAGR), but they are related.