Year	Number of
1990	56.07
1991	55
1992	56.02
1993	56.16
1994	57.12
1995	59.98
1996	57.31
1997	54.42
1998	52.13
1999	49.7
2000	49.68
2001	48.63
2002	46.45
2003	45.88
2004	45.22
2005	45.03
2006	44.91
2007	45.25
2008	46.33
2009	46.86
2010	46.3
2011	47.53
2012	48.82
2013	50.38
2014	51.82
2015	53.25
2016	54.69