Year	Number of
1990	55.47
1991	57.37
1992	59.27
1993	61.2
1994	63.2
1995	65.32
1996	67.67
1997	70.12
1998	72.68
1999	75.32
2000	78.09
2001	81.18
2002	84.45
2003	87.88
2004	91.43
2005	95.15
2006	98.67
2007	102.16
2008	105.83
2009	109.65
2010	113.73
2011	117.72
2012	121.93
2013	126.24
2014	130.71
2015	135.38
2016	140.7