Year	Number of
1990	33.77
1991	34.22
1992	34.12
1993	35.34
1994	35.63
1995	36.74
1996	38.23
1997	41.44
1998	41.85
1999	42.5
2000	45.78
2001	43.06
2002	44.77
2003	47.07
2004	49.77
2005	51.68
2006	52.52
2007	55.82
2008	57.58
2009	59.21
2010	61.12
2011	60.83
2012	61.67
2013	63.33
2014	64.45
2015	65.53
2016	61.96