YoY (Year-over-Year)

YoY (Year-over-Year) is generally not a standalone forecasting model like ARIMA or ETS. Instead, it is a comparison method used to measure how a value has changed relative to the same period one year earlier. In official statistical practice, year-over-year change means comparing a month or quarter with the corresponding month or quarter of the previous year, rather than comparing adjacent periods.

This method is especially useful when working with seasonal data. By comparing the same period across two consecutive years, YoY helps reduce the distortion caused by recurring seasonal patterns such as holidays, weather conditions, or regular business cycles. For that reason, it is widely used in economic and financial analysis to show underlying growth or decline more clearly.

In predictive analytics, YoY is typically used as a growth indicator, a derived variable, or an input feature for further modelling. It can also serve as a benchmark for interpreting trends and performance over time. While it is often included in analytical and forecasting workflows, it is better understood as a way of expressing annual change than as a forecasting technique in its own right.