Year	Number of
1990	40.3
1991	42.51
1992	44.86
1993	47.31
1994	49.88
1995	52.63
1996	53.03
1997	53.39
1998	53.78
1999	54.31
2000	55.03
2001	56.56
2002	58.28
2003	60.18
2004	62.25
2005	64.48
2006	65.89
2007	67.31
2008	68.96
2009	70.74
2010	72.72
2011	75.53
2012	78.57
2013	81.96
2014	85.5
2015	89.21
2016	93.19