Year	Number of
1990	117.49
1991	123.11
1992	129.38
1993	136.36
1994	143.98
1995	152.31
1996	161.97
1997	172.57
1998	184.39
1999	197.11
2000	210.83
2001	224.19
2002	238.73
2003	254.99
2004	272.73
2005	292.23
2006	307.91
2007	324.89
2008	343.61
2009	364.53
2010	387.98
2011	408.72
2012	431.36
2013	455.2
2014	481.52
2015	510.59
2016	542.44