Year	Number of
1990	48.05
1991	50.56
1992	53.23
1993	56.21
1994	59.36
1995	62.71
1996	65.85
1997	69.15
1998	72.96
1999	76.91
2000	81
2001	85.4
2002	90
2003	95.2
2004	100.69
2005	106.56
2006	112.71
2007	119.21
2008	126.16
2009	133.55
2010	141.47
2011	148.29
2012	155.58
2013	163.25
2014	171.27
2015	179.62
2016	188.28