Year	Number of
1990	44.92
1991	44.9
1992	44.72
1993	44.52
1994	44.46
1995	44.67
1996	45.36
1997	46.36
1998	47.71
1999	48.46
2000	49.12
2001	49.64
2002	50.68
2003	51.76
2004	52.81
2005	54.01
2006	55.49
2007	57.08
2008	58.68
2009	60.15
2010	61.88
2011	63.16
2012	65.32
2013	66.65
2014	68.28
2015	69.98
2016	72.12