YOY
From ACT Wiki
Year On Year, particularly in the context of percentage growth.
For example if revenues have grown as follows: Year 1: $100m Year 2: $110m Year 3: $132m
The related YOY percentage growth figures are calculated as: Years 1-2: [110-100=10]/100 - 1 = 10% Years 2-3: [132-110=22]/110 = 20%.
Also known as Y/Y.