Year	Number of
1990	54.59
1991	59.33
1992	63.74
1993	68.11
1994	72.9
1995	78.18
1996	83.28
1997	88.83
1998	94.68
1999	100.8
2000	107.51
2001	114.71
2002	122.76
2003	131.63
2004	141.14
2005	151.44
2006	159.68
2007	168.05
2008	176.74
2009	185.94
2010	195.89
2011	204.26
2012	213.03
2013	222.37
2014	231.95
2015	241.86
2016	252.23