Year	Number of
1990	52.58
1991	53.63
1992	54.81
1993	56.03
1994	57.5
1995	58.67
1996	59.94
1997	61.14
1998	62.03
1999	63.12
2000	64.32
2001	65.05
2002	64.86
2003	65.5
2004	65.57
2005	66.34
2006	67.18
2007	67.53
2008	69.5
2009	71.02
2010	72.72
2011	74.79
2012	76.7
2013	78.8
2014	80.95
2015	83.28
2016	85.62