# What is the meaning of "rolling" here?

What is the meaning of "rolling" or "rolling rate" here?

This chart shows a rolling 12-month rate of installs by country/region.

• Are you displaying a chart? Did you check what rolling means in general? Commented Jun 1, 2020 at 13:45
• It means yearly, beginning at any month. Commented Jun 1, 2020 at 17:08

To put it in layman's terms, as it is updated with more more current data, an equal time period "rolls off" the report.

For example, in a 12-month rolling report, the column or report for January 2020 would have information for Feb 2019 - Jan 2020. The column for Feb 2020 would have Mar 2019 - Feb 2020

Here Rolling is used in the context of a rolling rate or a rolling average. This is an averaged calculated for a period that is updated on a regular basis. The average itself is over just 12 months. As a new month's data comes the numbers from the oldest month are removed.

From bizfluent.com A regular 12-month average reduces a year of monthly figures into a single average number. A 12-month rolling average, or moving average, is simply a series of 12-month averages over multiple consecutive 12-month periods. This statistical tool can help you gauge the overall direction of a series of monthly data, because it smooths out the effects of month-to-month changes.

• I might guess that a rolling 12-month average would have the average of months 1 to 12, then the average of months 2 to 13, then the average of months 3 to 14, and so on. Commented Jun 1, 2020 at 15:26
• Your first paragraph describes it correctly: “As a new month’s data comes, the numbers from the oldest month are removed” But your quote in the second paragraph is incorrrect. The 12-month periods are not consecutive. In other words, the beginning of the second period does not start after the end of the first. I would find a better quote.
– Jim
Commented Jun 5, 2020 at 21:43
• @Jim; Thank you for looking. I understand that the averaging periods are actually consecutive months over a sequence of 12. This is what is meant by the quote though it sounds more like a moving yearly average since it always refers to months as 12-months. Commented Jun 6, 2020 at 15:35