Year	Number of
1990	168.14
1991	163.09
1992	162.19
1993	161.78
1994	162.82
1995	162.64
1996	160.41
1997	155.78
1998	151.31
1999	149.6
2000	151.47
2001	153.25
2002	156.96
2003	158.5
2004	162.3
2005	166.21
2006	169.71
2007	176.79
2008	181.66
2009	188.96
2010	195.44
2011	198.1
2012	201.59
2013	206.07
2014	210.96
2015	216.46
2016	223.7