Year	Number of
1990	37.96
1991	38.84
1992	39.78
1993	40.8
1994	41.89
1995	43.11
1996	42.99
1997	42.95
1998	42.98
1999	43.07
2000	43.25
2001	43.55
2002	43.93
2003	44.39
2004	44.9
2005	45.48
2006	46.27
2007	47.1
2008	48.06
2009	49.09
2010	50.24
2011	51.75
2012	53.39
2013	55.08
2014	56.92
2015	58.93
2016	61.07