Year	Number of
1990	24.04
1991	25.83
1992	27.82
1993	29.99
1994	32.57
1995	35.45
1996	37.06
1997	38.62
1998	40.57
1999	43.02
2000	45.81
2001	46.93
2002	48.11
2003	49.3
2004	50.58
2005	51.96
2006	53.71
2007	55.56
2008	57.55
2009	59.69
2010	62.02
2011	63.99
2012	66.08
2013	68.3
2014	70.64
2015	73.1
2016	78.38