Table 4.

Number of participating countries by starting year of trials

Number of countries	Number of trials (N = 333*)
	-2000	2001-2005	2006-2010	Total
Single country	19	73	135	227	(68.2%)
Multiple countries	16	40	50	106	(31.8%)
2-5 countries	8	14	13	35	(10.5%)
6-20 countries	7	10	20	37	(11.1%)
> 20 countries	1	16	17	34	(10.2%)

* 11 trials whose starting years or countries were unknown were excluded.