Year-over-year (YOY)—sometimes referred to as year-on-year—is a frequently used financial comparison for looking at two or more measurable events on an annualized basis. Observing YOY performance allows for gauging if a company’s financial performance is improving, static, or worsening. For example, you may read in financial reports that a particular business reported that its revenues increased for the third quarter on a YOY basis for the last three years.