Year	Number of
1990	47.49
1991	49.3
1992	51.39
1993	53.7
1994	56.17
1995	58.76
1996	60.69
1997	62.65
1998	64.67
1999	66.9
2000	69.46
2001	72.16
2002	75.2
2003	78.6
2004	82.3
2005	86.33
2006	90.17
2007	94.21
2008	98.61
2009	103.32
2010	108.43
2011	112.52
2012	116.86
2013	121.36
2014	126.18
2015	131.34
2016	136.84