Year	Number of
1990	52.52
1991	54.64
1992	57.53
1993	61.31
1994	66.87
1995	73.57
1996	73.62
1997	77.73
1998	82.3
1999	86
2000	90.3
2001	91.48
2002	93.73
2003	96.8
2004	104.13
2005	107.98
2006	115.78
2007	115.55
2008	119.95
2009	126.05
2010	131.17
2011	140.9
2012	146.22
2013	153.37
2014	159.27
2015	165.34
2016	173.08