Year	Number of
1990	48.83
1991	50.58
1992	53.22
1993	56.23
1994	59.22
1995	62.08
1996	64.53
1997	68.04
1998	72.02
1999	73.88
2000	77.52
2001	81.19
2002	85.81
2003	90.1
2004	94.26
2005	99.14
2006	103.3
2007	108.28
2008	113
2009	119.25
2010	125.94
2011	130.9
2012	137.09
2013	142.81
2014	148.07
2015	153.22
2016	158.3