What does the "year-on-year" mean?

Native speaker’s answer
Rebecca
"Year-on-year" means from year to year; with every year that passes. It's usually used when you want to make financial comparisons each year against the other years. It's also sometimes used as a formula. Ex: Our year-to-year sales have increased in the last three years. Ex: There will be continual year-on-year vaccine development.