YoY is a financial term used to assess the growth or decline of a particular variable over a twelve-month period.1 It is a type of financial analysis used for comparing time series data and is useful for measuring growth and detecting trends.2 The formula to calculate YoY is the current year's value divided by the previous year's value minus one.3 YoY analysis can be applied to various financial metrics such as revenue, profit, and market share to evaluate a company's performance over the past year.