Table 6. Collaboration measures.

Measure	Q1	Q2	Q3	Q4	Q5	Q6	Q7
	1980–84	1985–89	1990–94	1995–99	2000–04	2005–09	2010–14
% collaborative articles	61.97	72.21	77.57	83.18	87.63	88.51	91.73
% single authored articles	38.03	27.79	22.43	16.82	12.37	11.49	8.27
n signatures	2,927	5,559	7,011	9,981	15,779	23,358	34,998
M (signatures per article)	2.43	2.90	3.22	3.62	4.03	4.30	4.79
SD (signatures per article)	1.67	1.88	2.05	2.34	2.91	3.14	3.81
maximum (range signatures per article)	10	13	17	23	80	98	176
% authors with only co-authors articles	79.20	83.07	86.04	89.24	92.00	93.99	95.76
% authors with only single-authored articles	13.88	9.46	6.97	4.27	3.14	2.61	1.88
% authors with co- and single-authored articles	6.92	7.47	6.99	6.45	4.87	3.40	2.36