What is year over year (YOY)? Explained

In financial analysis and data analytics, YOY is the acronym for year over year. YOY indicates the change from the comparable amount reported in the same period one year earlier. Below are three examples of YOY.A retailer’s sales for the first 5 weeks of the current fiscal year are $206,000, which is a 3% increase YOY. In other words, the sales in the first 5 weeks of this fiscal year are 3% greater than the sales in the first 5 weeks of the previous fiscal year. Based on this statement, the sales in the first 5 weeks of the previous fiscal year must have been $200,000. [$206,000 minus $200,000 is a $6,000 increase YOY. The $6,000 YOY increase divided by $200,000 is a 3% increase YOY.]

A church received contributions of $5,500 during Week #16 of its current year, which is a 10% increase YOY. In other words, the contributions during Week #16 of this year are 10% greater than those of Week #16 of the previous year (which must have been $5,000). [$5,500 minus $5,000 is a $500 increase YOY. The $500 increase divided by $5,000 is a 10% increase YOY.]

A website had 88,000 page views on the second Monday of January, which was a 12% decrease YOY. This means that the page views of the second Monday of January of the previous year were 100,000. [88,000 page views minus the previous year’s 100,000 page views is a 12,000 decrease in page views YOY. The 12,000 decrease divided by 100,000 is a 12% decrease YOY.]