Year	Number of
1990	54.16
1991	55.26
1992	56.49
1993	57.83
1994	59.27
1995	60.88
1996	61.65
1997	62.55
1998	63.5
1999	64.49
2000	65.58
2001	65.67
2002	65.84
2003	66.11
2004	66.51
2005	67.13
2006	68.21
2007	69.42
2008	70.89
2009	72.43
2010	74.06
2011	75.42
2012	76.85
2013	78.31
2014	79.88
2015	81.61
2016	83.46