(used especially when talking about figures, prices, etc.) each year, compared with the last year :
Spending has increased year on year.
a year-on-year increase in spending
(used especially when talking about figures, prices, etc.) each year, compared with the last year :
Spending has increased year on year.
a year-on-year increase in spending
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005