The impact of scientific career duration on evaluating researchers' scientific productivity: The case of Iran's papers indexed in SCI during 1991-2011

Researchers with different scientific career durations vary in their scientific productivity. Therefore, it is necessary to normalize their publication numbers by their scientific career durations in order to have a more objective comparison among researchers. The present study attempts to verify the impact of scientific career duration on research evaluation using scientometrics method. To do so, it compares Iranian researchers' publication rates in various disciplines covered in the Science Citation Index (SCI) during the period of 1991-2011. The analysis concentrates on those Iranian, who are corresponding authors, with long scientific career durations. The results show that the disciplines significantly vary in their researchers' scientific career durations and their crude number of papers. However, no significant difference was observed in the researchers' publication rates when the comparisons are limited to 21-year SCD researchers, the dominant group of the sample. In other words, the differences observed between many disciplines in their scientific productivity would disappear after normalizing the publication counts by authors' scientific career duration. This implies that comparison among scientists would be reasonable only if they are of the same area of expertise and in similar phases of their scientific lives. It is of special importance to those studies on research assessment that concentrate on a single year or a limited time period.