Year	Number of
1990	19.02
1991	19.53
1992	19.95
1993	20.4
1994	20.82
1995	21.34
1996	21.87
1997	22.45
1998	22.28
1999	24.47
2000	25.81
2001	27.55
2002	29.33
2003	30.94
2004	31.64
2005	32.86
2006	33.92
2007	35.51
2008	37.31
2009	39.56
2010	42.87
2011	46.24
2012	48.38
2013	50.52
2014	54.34
2015	57.61
2016	60.58