Year	Number of
1990	42.77
1991	42.36
1992	42.51
1993	42.41
1994	42.6
1995	42.48
1996	42.48
1997	41.47
1998	41.13
1999	42.21
2000	43.53
2001	45.05
2002	45.73
2003	46.73
2004	48.22
2005	49.08
2006	49.74
2007	50.41
2008	51.6
2009	52.83
2010	53.93
2011	55.16
2012	56.49
2013	57.84
2014	59.04
2015	60.44
2016	62.02