Year	Number of
1990	131.89
1991	139.37
1992	148.19
1993	158.15
1994	168.25
1995	178.15
1996	184.95
1997	190.69
1998	195.24
1999	199.75
2000	204.64
2001	207.74
2002	210.82
2003	213.9
2004	217.43
2005	221.6
2006	227.15
2007	233.35
2008	240.53
2009	248.44
2010	257.12
2011	265.11
2012	273.54
2013	282.15
2014	291.53
2015	301.81
2016	313.79