Year	Number of
1990	26.56
1991	27.97
1992	29.53
1993	31.29
1994	33.24
1995	35.4
1996	38.81
1997	42.68
1998	47.01
1999	51.68
2000	56.67
2001	61.53
2002	66.5
2003	71.76
2004	77.54
2005	84.04
2006	87.63
2007	91.54
2008	96.1
2009	100.94
2010	106.06
2011	113.88
2012	122.4
2013	131.76
2014	141.9
2015	152.88
2016	165.16