Year-Over-Year (YOY)

What Is Year-Over-Year (YOY)?

Year-Over-Year (YOY) is a frequently used financial comparison for comparing two or more measurable events on an annualized basis.

Looking at YOY performance allows for gauging if a company's financial performance is improving, static, or worsening. For example, in financial reports, you may read that a particular business reported its revenues increased for the third quarter, on a YOY basis, for the last three years.

Understanding Year-Over-Year

Year-over-year (sometimes referred to as year-on-year) comparisons are a popular and effective way to evaluate the financial performance of a company and the performance of investments. Any measurable event that repeats annually can be compared on a YOY basis. Common YOY comparisons include annual, quarterly, and monthly performance.

Benefits of Year-Over-Year

YOY measurements facilitate the cross-comparison of sets of data. For a company's first-quarter revenue using YOY data, a financial analyst or investor can compare years of first-quarter revenue data and quickly ascertain whether a company’s revenue is increasing or decreasing.

For example, in the first quarter of 2021, the Coca-Cola corporation reported a 5% increase in net revenues over the first quarter of the previous year. By comparing the same months in different years, it is possible to draw accurate comparisons despite the seasonal nature of consumer behavior. This YOY comparison is also valuable for investment portfolios. Investors like to examine YOY performance to see how performance changes across time.

Reasoning Behind Year-over-Year

YOY comparisons are popular when analyzing a company's performance because they help mitigate seasonality, a factor that can influence most businesses. Sales, profits, and other financial metrics change during different periods of the year because most lines of business have a peak season and a low demand season.

For example, retailers have a peak demand season during the holiday shopping season, which falls in the fourth quarter of the year. To properly quantify a company's performance, it makes sense to compare revenue and profits year-over-year.

It's important to compare the fourth-quarter performance in one year to the fourth-quarter performance in other years. If an investor looks at a retailer's results in the fourth quarter versus the prior third quarter, it might appear a company is undergoing unprecedented growth when it is seasonality that is influencing the difference in the results.

Similarly, in a comparison of the fourth quarter to the following first quarter, there might appear a dramatic decline when this could also be a result of seasonality.

YOY also differs from the term "sequential," which measures one quarter or month to the previous one and allows investors to see linear growth. For instance, the number of cell phones a tech company sold in the fourth quarter compared to the third quarter, or the number of seats an airline filled in January compared to December. 

Real-World Example

In a 2019 NASDAQ report, Kellogg Company released mixed results for the fourth quarter of 2018, revealing that its year-over-year earnings continue to decline, even while sales have increased following corporate acquisitions. Kellogg predicts that adjusted earnings will drop by a further 5% to 7% in 2019, as it continues to invest in alternate channels and pack formats.

The company has also revealed plans to reorganize its North America and Asia-Pacific segments, removing several divisions from its North America segment and reorganizing its Asia-Pacific segment into Kellogg Asia, Middle East, and Africa. Despite decreasing year-over-year earnings, however, the company’s solid presence and responsiveness to consumer consumption trends mean that Kellogg’s overall outlook is favorable.

What Is Year-Over-Year Used for?

YOY is used to make comparisons between one time period and another that is one year earlier. This allows for an annualized comparison, for example between third-quarter earnings this year vs. third-quarter earnings the year earlier. It is commonly used to compare a company's growth in profits or revenue and it can also be used to describe yearly changes in an economy's money supply, gross domestic product (GDP), or other economic measurements.

How Is Year-Over-Year Calculated?

YOY calculations are straightforward and usually are expressed in percentage terms. This would involve taking the current year's value and dividing it by the prior year's value and subtracting one: (this year)/(last year) - 1.

What's the Difference Between YOY and YTD?

YOY looks at a 12-month change. Year-to-date, or YTD, looks at a change relative to the beginning of the year (usually January 1st).

What If I Am Interested in Comparisons for Less Than a Year?

You can compute month-over-month (MoM) or quarter-over-quarter (QoQ) in much the same way as YOY, and for any other timeframe you desire.