Year	Number of
1990	25.74
1991	27.03
1992	27.97
1993	28.83
1994	30.38
1995	32.12
1996	34.27
1997	35.29
1998	37.03
1999	38.34
2000	39.98
2001	41.33
2002	42.14
2003	42.71
2004	43.07
2005	43.5
2006	44.64
2007	45.95
2008	47.5
2009	49.07
2010	50.71
2011	52.32
2012	53.93
2013	55.56
2014	57.15
2015	58.29
2016	60.53