Circulation is a count of how many copies of a particular publication are distributed. Circulation audits are provided by the Audit Bureau of Circulations (ABC).

Readership is an estimate of how many readers a publication has. As most publications have more than one reader per copy, the NRS readership estimate is very different from the circulation count.

Readership estimates also show:

• The demographic profile of readers.
• What else they read and do.

The relationship between readership and circulation is known as readers-per-copy, i.e. readership divided by circulation. The number of readers-per-copy varies considerably by publication, as the following examples show.

The relationship between readership and circulation is a complex one. Long-term trend data show a strong relationship between the two, but there can be changes, both sudden and gradual.

For instance, the chart below shows the changing relationship between readership and circulation for Heat magazine as the number of readers-per-copy increases over time.

In some cases, sudden period-on-period changes are a result of sample variation, particularly for smaller titles. However, around half of the period-on-period changes in readers-per-copy are statistically significant and it is important that the NRS reflects these real changes in reader-per-copy. (Please click here for information about how to test if a period-on-period difference in readership is statistically significant).

Some examples of the reasons for real changes on readers-per-copy are shown below:

Examples of sudden changes:

• Heavy promotional activity (e.g free gift)
• Price cuts
• Major changes to editorial format
• Sudden losses or gains in circulation
• Seasonal factors

Examples of gradual changes:

• Awareness of new titles can take time to grow
• Long-term expansion or contraction of circulation
• Changes in profile (e.g ageing readership)
• Launch and closure of competitive titles
• Impact of digital media

There are many other possible reasons why readers-per-copy can change over time. Please click here for a more detailed examination of the subject.

NRS has produced a series of charts showing trends in readership estimates and circulation data for the past 8 years. The purpose of these charts is to demonstrate the relationship between readership and circulation over time, where there are similarities between the two, and where there are differences.

The charts show that for a very large majority of titles on NRS, there is a close correlation between readership and circulation over time. The conclusion is that NRS estimates provide as reliable an indication of readership trends as ABC data provides trends of circulation.

There are a number of examples where readership appears to be following a different trend to circulation for all or part of the 8-year period. There are many reasons why in certain circumstances readership and circulation will diverge: an explanation of these circumstances is given here.

There is a separate chart for each title: click here to view an alphabetical listing of the titles covered. A sample chart is shown below. Each chart plots Average Issue Readership (All Adults) and Circulation (UK only, or UK & Eire, whichever is available) across the 8-year period 2001-2008.

Each chart has two vertical axes, the left one for readership, and the right one for circulation. These axes are scaled in such a way that the readership and circulation plot-lines both appear in the same area of the chart, so that any period-on-period changes in either can be easily seen and visually compared.

NB For the purpose of this exercise, the full ABC figures have been entered into the spreadsheets for plotting the circulation trends and calculating the readers-per-copy, but the circulation figures displayed in the tables have been rounded to the nearest whole 1,000. For the actual certified ABC figures, please visit the ABC website at www.abc.org.uk

If you have any questions about these charts and their findings, please contact NRS Ltd.