Pressure to publish: A Bibliometric Study of PhD-Students (1993-2009)

Introduction
Academic advancements as well as funding depend on publications and thus pressure researchers to publish. The perception of the pressure to publish is tied to career stage. The uncertain future careers of PhD-students and postdocs cause them to be more aware of publication pressure and may to lead to a practice of splitting scientific findings into smaller units to maximize the research output.

Method
Using a data set of health sciences PhD-students from the University of Southern Denmark, this paper investigates whether the productivity and citation impact of PhD-students has increased over time. We use a pseudo-experimental matching method to ensure that former and contemporary PhD students have similar characteristics as measured by a number of balancing variables.

Analysis
The matching method enables us to estimate productivity and impact by an ordinary t-test using standard statistical software packages.

Results
Collectively, after completion of the PhD-program the PhD students from the new cohort published more than the PhD students from the old cohort. The results of the citation analyses show that on average, the publications by the new cohort from years 1 through 5 after graduation receive more citations than the publications from the old cohort. Yet, when comparing normalized and fractionalized citation counts, the cohorts are remarkably similar.

Conclusion
PhD-students have increased their publication rate although the citation rates have not changed.