Year	Number of
1990	28.01
1991	30.48
1992	32.94
1993	35.6
1994	38.74
1995	42.67
1996	44.91
1997	47.65
1998	50.86
1999	54.43
2000	58.3
2001	61.53
2002	65.41
2003	70.26
2004	76.5
2005	84.69
2006	91.79
2007	100.67
2008	111.39
2009	123.81
2010	137.87
2011	152.22
2012	168.39
2013	186.09
2014	205.02
2015	225.14
2016	245.01