  Accurate measurement of institutional research productivity should account
for the real contribution of the research staff to the output produced in
collaboration with other organizations. In the framework of bibliometric
measurement, this implies accounting for both the number of co-authors and each
individual's real contribution to scientific publications. Common practice in
the life sciences is to indicate such contribution through the order of author
names in the byline. In this work, we measure the distortion introduced to
university-level bibliometric productivity rankings when the number of
co-authors or their position in the byline is ignored. The field of observation
consists of all Italian universities active in the life sciences (Biology and
Medicine). The analysis is based on the research output of the university staff
over the period 2004-2008. Based on the results, we recommend against the use
of bibliometric indicators that ignore co-authorship and real contribution of
each author to research outputs.
