Year	Number of
1990	29.69
1991	30.14
1992	31.11
1993	32.22
1994	32.78
1995	33.98
1996	34.24
1997	34.6
1998	35.39
1999	34.91
2000	35.61
2001	35.63
2002	36.04
2003	37.12
2004	37.91
2005	38.76
2006	39.11
2007	39.08
2008	40.32
2009	41.38
2010	42.91
2011	44.75
2012	46.96
2013	50.11
2014	53.19
2015	55.85
2016	58.74