Year	Number of
1990	58.81
1991	61.03
1992	63.44
1993	66.11
1994	68.92
1995	72.01
1996	75.28
1997	78.92
1998	82.62
1999	84.54
2000	87.18
2001	90.51
2002	92.12
2003	95.47
2004	98.47
2005	102.08
2006	105.85
2007	109.57
2008	112.87
2009	117.29
2010	120.62
2011	123.2
2012	127.05
2013	130.94
2014	135.21
2015	139.75
2016	144.76