Year	Number of
1990	215.4
1991	216.81
1992	215.24
1993	213.9
1994	215.25
1995	215.48
1996	211.62
1997	210.66
1998	211.52
1999	210.9
2000	206.02
2001	199.22
2002	188.44
2003	185.09
2004	181.84
2005	180.91
2006	179.57
2007	174.39
2008	177.52
2009	178.72
2010	173.99
2011	172.87
2012	171.1
2013	168.11
2014	167.78
2015	169.3
2016	170.84