Year	Number of
1990	36.22
1991	37.1
1992	37.66
1993	38.91
1994	41.22
1995	42.45
1996	44.87
1997	45.85
1998	47.45
1999	49.82
2000	51.52
2001	53.89
2002	53.65
2003	55.77
2004	57.32
2005	56.39
2006	57.2
2007	55.67
2008	56.47
2009	56.12
2010	54.62
2011	55.37
2012	55.24
2013	54.71
2014	55.21
2015	55.98
2016	56.69