Year	Number of
1990	26.14
1991	27.39
1992	28.73
1993	30.26
1994	32.02
1995	34.18
1996	36.66
1997	39.34
1998	44.05
1999	49.91
2000	53.7
2001	56.36
2002	59.66
2003	64.24
2004	71.95
2005	77.94
2006	81.5
2007	84.41
2008	89.32
2009	95.56
2010	103.03
2011	112.33
2012	120.71
2013	130.77
2014	141.24
2015	149.4
2016	158.42