Table. Overview of publication activity.

	1998	2004	2008	P value
Total number of doctoral candidates evaluated in the study	264	316	316	–
Total number of publications	207	254	439	0.081
of which case reports	26 (12.6%)	18 (7.1%)	34 (7.7%)
95 %-confidence interval	(8.1%17.1%)	(3.9%–10.3%)	(5.2%–10.2%)
Number of publications per doctoral candidate (all)	0.78	0.8	1.39	<0.001
Standard deviation	1.777	1.733	2.458
Median (interquartile range)	0 (0–1)	0 (0–1)	1 (0–2)
Number of doctoral candidates who have published	86 (33%)	124 (39%) (	165 (52%)	<0.001
95 %-confidence interval	(27.3%–38.7%)	33.6%–44.4%)	(46.5%–57.5%)
Number of publications per publishing doctoral candidate	2.41	2.05	2.66	0.023
Standard deviation	2.413	2.263	2.864
Median (interquartile range)	2 (1–3)	1 (1–2)	2 (1–3)
Average impact factor per publication at the time of publication	2.421*1	3.658*2	3.622*3	<0.001
Standard deviation	2.363	3.445	3.373
Median (interquartile range)	1.65 (0.79–3.28)	2.78 (1.63–4.99)	2.96 (1.88–4.45)
Average current impact factor per publication	3.131*1	4.275*2	3.853*3	0.005
Standard deviation	2.415	4.283	3.485
Median (interquartile range)	2.61 (1.40–4.60)	3.08 (2.03–6.01)	3.12 (2.10–4.85)
Number of first authorships	56 (27%)	67 (26.4%)	111 (25.3%)	0.879
95 %-confidence interval	(20.9%–33.1%)	(21.0%–31.8%)	(21.2%–29.4%)
of which case reports	15	11	19
(proportion of publications with first authorship)	(26.8%)	(16.4%)	(17.1%)
Number of last authorships	8 (3.9%)	4 (1.6%)	6 (1.4%)	0.103
95 %-confidence interval	(0%–10.2%)	(0%–3.1%)	(0%–2.5%)
of which case reports	3	1	0
(proportion of publications with last authorship)	(37.5%)	(25%)	(0%)

^*1For 11 publications and their journals, no impact factor was available;^*2for 12 publications and their journals, no impact factor was available; ^*3for 23 publications and their journals, no impact factor was available; case reports were included in the statistical calculations but usually not related to the doctoral thesis