Year on year
Definition 1 of 1
Pro Tip 1/3Measurement of Change
Used to discuss changes in quantities or amounts compared to the previous year. 
Her blog's readership has increased year on year.
Pro Tip 2/3Business Context
Often appears in financial or business reports to illustrate trends. 
Our sales figures show a year on year growth of 15%.
Pro Tip 3/3Comparative Nature
Implies a direct comparison rather than a general statement about increase or decrease. 
The production costs have gone down year on year.