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Distributing Print Exposures Through Time Written by Guy Consterdine, Guy Consterdine Associates
Britain has a new tool to improve the planning of print media schedules – the National Readership Survey’s readership accumulation study, published in 2004. It provides estimates, publication by publication, of the rates at which the readership of individual issues of newspapers and consumer magazines build over time. A more realistic assessment can therefore be made of the day by day, or week by week, distribution of a print campaign’s audience.
The flighting of print and television ad exposures can be planned in the same way as each other, simultaneously. In effect, print can be treated like a broadcast medium as far as media scheduling is concerned. Campaigns can be planned with weekly target points, weekly reach estimates, and weekly weight goals.
Consequently the way publishers are viewing the survey is that the time has never been better for magazines and newspapers to capture a larger share of media-mix budgets.
Summary of method
The survey was conducted by NOP World, using NOP in London for the fieldwork and sister company MRI in New York for the editing and modelling. MRI had previously conducted an accumulation survey of its own in the USA, and obtained curves that were broadly similar to those found in Britain.
The sample of adults was recruited through the NOP Random Location Omnibus Survey. In a representative sub-sample of Omnibus interviews, respondents were asked to keep a diary of their reading of newspapers and magazines for one week. 70% agreed to do so. At the end of the week interviewers collected the completed diaries, or where it was not possible to collect them the diaries were posted back to NOP. Among those who agreed to participate, 60% successfully returned a usable diary. This amounted to 7,001 diaries.
Every day, for each publication read, respondents entered in the diaries the cover date of the issue as shown on the front page, indicated whether it was their own/household copy, and stated whether or not it was the first time that particular issue had been read. A sample page of the diary is reproduced in miniature on the right.
The completed diaries were shipped to New York for analysis by MRI. The diaries first went through an editing process in which logical consistency checks were made on the entries. There was no demographic weighting of the data, but weights were applied for primary and secondary readership, so that the profile of primary/secondary readership recorded for each title matched its NRS profile of primary/secondary readers.
The key measure was ‘first time reading’ (FTR) – that is, a reading event that the diarist recorded as being the first time he or she had read that particular issue. This measure was chosen by NRS because it logically fits the nature of NRS average-issue readership data. The main NRS survey only counts a reader once, regardless of how many times he or she picks up the same copy of a publication; and potential exposure to the advertising is delivered on the first time of reading. (QRS, the Quality of Reading Survey, suggests that approximately 70% of all pages are indeed opened on the first day of reading, on average.)
For every ‘first time reading’ event recorded in the diaries, the time-lag was calculated: that is, the number of days that had elapsed since that specific issue first became available. Consolidating these time-lags across all issues and all diaries produced the raw data for curve-fitting, by publication.
The diary data, being very different in kind from the standard NRS readership measures, were not intended to produce readership levels identical to those of the NRS in an absolute sense. Instead, the diary data simply had the objective of being a means of distributing through time the exposures which the NRS was reporting. Consequently the accumulation curves were designed so that on the vertical scale they eventually finished at 100%, where 100% is the NRS average-issue readership figure for a given publication.
The horizontal axis for the curves represented the number of days since the title first appeared. Day 1 was defined as the first appearance day. All curves started at day 1; any readership that occurred before then was allocated to day 1, for convenience. The axis extended to six months (day 181). Any curves which had not quite reached 100% by day 181 had the outstanding accumulation attributed to day 182+.
Curves plotted using the raw data inevitably showed some uneven-ness because of sampling variation on relatively modest sample sizes. Therefore MRI modelled accumulation curves for all publications and publication groups, thus smoothing out the bumpiness of the raw data, in order to produce curves which represent good predictions of future behaviour. The modelling used a number of different mathematical formulae, choosing the one that best fitted the raw data for each specific curve.
130 ‘first time reading’ events (FTRs) was set as the minimum sample size on which to base an accumulation curve. Any publication which achieved 130 or more FTRs would have a curve based solely on its own data. A publication with less than 130 FTRs would use all of its own FTRs and the shortfall below 130 would be made up by a contribution from the curve for the publication group to which it belonged (such as women’s weeklies or motoring monthlies). Any title with no FTRs of its own would simply use its group curve.