L E T T E R S T O T H E E D I T O R
The letter below was received in response to the article, "Measuring Citation Advantages of Open Accessibility", by Samsoon C. Soong, Hong Kong University of Science and Technology, in the November/December 2009 issue of D-Lib Magazine.
I'm writing with regard to the following article: "Measuring Citation Advantages of Open Accessibility" to say that I'm not at all convinced by this research.
My main criticism of this paper is related to the calculation of an average citation per year value before and after the article was made available in the repository. We should all be aware that articles have a characteristic citation lifespan: they are published, citations build slowly at first, then accelerate, then peak, then decline over a period of time. This curve will have a different shape depending on the subject area that the article is related to. Comparing an average citation per year at different points on this citation curve is not very sensible, especially where the number of years in each status (i.e. before or after deposit in a repository) varies from article to article. Comparing different subjects together confounds the data even further. I would speculate that the 'finding' is due to nothing more than chance, and I'd even go further to say that by not displaying the % decreases when the average citation count goes down between the two periods (instead the unquantified text ' No increase' is used), this paper is clearly biased towards finding a positive OA effect.
Iain Craig, John Wiley & Sons
Below is Samson C. Soong's response to the letter from Iain Craig.
Receiving critical feedback on my study from an expert in bibliometric analysis feels uncomfortable, yet it is also gratifying. It re-confirms my belief that good study design, simple or sophisticated, is important.
With a number of intervening variables that are uncontrolled or that cannot be straightforwardly or cleanly controlled, including some factors mentioned by Mr. Craig, my study indeed may suffer from some statistical confounding. It goes without saying that there is frequently a trade-off between a study designed to be conducted as economically as possible, which then may not necessarily be problem-free, and more sophisticated ones that therefore are also more expensive to conduct.
For my study focusing on whether or not there might be a possible citation advantage to open access publication, I did not see the need to calculate and display the percentage of decrease that obviously did not result from open accessibility or greater visibility. I shared my study data candidly and non-selectively. At the same time, in my concluding remarks, I encouraged further studies on this topic while making clear that personally I do support the open access movement.
Samson C. Soong, The Hong Kong University of Science and Technology
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