Comparing NADbank Studies-Newsletter

Users typically compare data from several NADbank Studies when evaluating newspaper readership. However, there are no hard and fast rules as to how the materials should be read and interpret. Users can look at changes from year-over-year (NADbank 2009 versus NADbank 2008) or during a specific period, using several consecutive studies (NADbank 2006, 2007, 2008 and 2009).

In general, newspaper readership is expressed as incidence or reach (percentage of adults 18+ who read newspapers) or number of readers. The decision to use incidence or number of readers depends on the user’s objective. The key question is whether the chosen metric provides adequate information.

It is important to consider the following:

1. When evaluating changes in newspaper readership, it is prudent to consider all measures, reach, number of readers, and changes in population over time.
2. The NADbank database is made up of a combination of full sample and blended or rolling sample and three-year data.

• Full sample data provides single year results.
• Data for rolling sample markets represents an “average” over the two-year period.
• Three-year data is only comparable against, the previous three years. For example, data collected in 2009 is comparable to data collected in 2006.

3. When sourcing NADbank data, clearly reference the source as NADbank and specify the year of the study. This avoids confusion and provides context for the reported data.
4. Incidence is the primary measure for estimating or projecting the results of a survey to a target population. It is especially important to understand the term incidence when comparing year to year results. Using absolute numbers (e.g. numbers of readers) may be misleading in that changes in population estimates can account for changes in the number of readers. There are times when survey results are reported with a margin of error. For example, a margin of error plus or minus 1.4 percentage points for read any newspaper yesterday in Toronto CMA may be cited in order to explain changing figures. Although this can be expressed in terms of population, margin of error is independent of population. Newspaper reach does not relate to the size of the group being measured. Changing the population base can result in an increase or decrease in the number of readers.

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• Importance of the Margin of Error