Year	Number of
1990	19.8
1991	21.73
1992	23.53
1993	25.53
1994	27.77
1995	28.65
1996	31.87
1997	32.87
1998	36.84
1999	40.5
2000	41.71
2001	45.55
2002	47.98
2003	48.24
2004	49.97
2005	50.23
2006	50.89
2007	54.48
2008	58.08
2009	59.9
2010	63.36
2011	63.49
2012	65.2
2013	69.19
2014	72.88
2015	74.22
2016	77.2