Year	Number of
1990	315.64
1991	320.94
1992	326.56
1993	332.66
1994	339.43
1995	347.14
1996	348.68
1997	351.05
1998	354.01
1999	356.91
2000	359.71
2001	367.21
2002	374.78
2003	382.9
2004	391.32
2005	400.39
2006	408.32
2007	416.52
2008	425.53
2009	435.74
2010	447.45
2011	459.98
2012	474.15
2013	488.89
2014	504.53
2015	520.86
2016	535.55