Year	Number of
1990	65.24
1991	68.99
1992	73.08
1993	77.57
1994	82.39
1995	87.6
1996	96.45
1997	106.45
1998	117.89
1999	130.79
2000	145.59
2001	150.9
2002	156.31
2003	161.9
2004	167.9
2005	174.45
2006	176.42
2007	178.82
2008	181.66
2009	184.78
2010	188.16
2011	199.6
2012	211.98
2013	225.34
2014	239.76
2015	255.35
2016	271.68