Year	Number of
1990	72.14
1991	73.91
1992	75.89
1993	78.23
1994	80.99
1995	83.6
1996	86.3
1997	89.28
1998	93.15
1999	95.27
2000	99.07
2001	102.36
2002	104.62
2003	110.55
2004	112.61
2005	116.62
2006	120.71
2007	125.89
2008	132.86
2009	136.6
2010	141.83
2011	144.49
2012	148.08
2013	152.37
2014	156.64
2015	161.1
2016	165.6