Year	Number of
1990	11
1991	11.75
1992	12.61
1993	13.57
1994	14.63
1995	15.72
1996	16.53
1997	17.39
1998	18.4
1999	19.57
2000	20.92
2001	21.76
2002	22.79
2003	24.12
2004	25.86
2005	28.12
2006	30.33
2007	33.21
2008	36.75
2009	40.56
2010	44.45
2011	48.27
2012	51.53
2013	54.36
2014	57.01
2015	59.66
2016	64.36