As independent measurers of readership in Ireland for over a decade and pioneers of many of the segmentation techniques now regarded as 'standard', we at TGI take more than a passing interest in the debate in the pages of recent issues of Marketing about the inter-relationship between measures of circulation and readership.

It is a debate that is also re-emerging in Britain and the US. The industry's concern seems to be founded on the belief that the relationship between the two measurements of the marketplace should be unchanging and predictable, a requirement due to the forward nature of the advertising-media industry.

But what if people's buying and reading behaviour does not accord with that industry requirement? What needs to change? Should this be the research methodology itself – which will only ever be a measure of past behaviour used to predict the future – or does there need to be a recognition that, in a highly dynamic market, past behaviour cannot be used as a simple way of predicting future behaviour?

In the press market, publishers purposely de-stabilise the reader loyalty of their own titles, and indeed competitive titles, through price wars, promotions and format changes. Such activity, in a market as healthily competitive as is the case in Ireland, must have positive and negative, often non-compensatory, effects throughout the market.

Consumers are responding to publishers' marketing activity. They are exercising consumer choice and because of this fluidity, the press market is turning into one much closer to television, where overnight ratings are used by traders to 'beat each other up' on a daily basis. Press buying will respond to the market changes as they happen.

Arising from this, there are three points worth considering:

Average issue readership should iron out the short term variations and contribute to the creation of a level price-negotiation playing field. Given that advertisers buy campaigns with multiple OTS, the number of times readership research underestimates exposure should be counterbalanced by the equal and opposite situation. In other words, the phenomenon of compensating errors on which all such estimations are built.

Secondly, circulation and readership do not march hand-in-hand at the same pace. They never have and they never will because consumers just do not operate like that. As readers per copy (RPC) figures are again an average, logically, only a certain proportion of copies of a publication actually gain that average level of exposure. The rest are above or below that average ands sometimes by a significant distance.

When circulation changes, it is not known where on that RPC spectrum that loss or gain occurs. It might be considered logical that an additional buyer would come from within the existing pool of secondary or tertiary readers, so lowering the average RPC.

Logic would also suggest that a lost sale might come from the pool of primary readers (whose actual pass on habits are unknown) or from 'corporate' sales as a cost cutting measure. So the average readers per copy could move in either direction.

Will compensating movements happen in both directions to leave the RPC unchanged? Who knows? They might do, but not necessarily in the same publication period, hence 'wobble'. That brings us to point three.

Target Group Index (TGI) in Ireland shows that the number of single person households has more than doubled in the last decade, as have two-person homes. For publications entering private households and never being read by anyone outside them, the RPC potential is down. It is a slow trend and at different speeds within various geographies and communities. So the effects will be patchy and probably unpredictable.

The survey also shows that attitudes to newspapers and the role they fill in peoples lives have also changed dramatically across that decade and again those changes will vary by sub-group of the population with often unpredictable effects. Such changes may well be fuelled by the inexorable rise in internet access.

Readership surveys do not set out to confuse. They are designed to do exactly the opposite. But we do know that the world is indeed a confusing place in which consumers are increasingly exercising their confidence and choice and, as a result, do not fall into the patterns of behaviour prevalent in the past.

Aisling Seery is group account manager for TGI Ireland