Year	Number of
1990	42.53
1991	42.55
1992	43.33
1993	43.82
1994	44.35
1995	44.99
1996	45.94
1997	46.87
1998	47.36
1999	47.42
2000	49.05
2001	48.61
2002	48.92
2003	48.43
2004	49.08
2005	50.08
2006	50.38
2007	50.5
2008	50.5
2009	50.09
2010	51.09
2011	51.69
2012	53.12
2013	54.44
2014	55.75
2015	57.1
2016	58.49