Year	Number of
1990	26.62
1991	27.28
1992	27.93
1993	28.51
1994	29.1
1995	29.8
1996	30.51
1997	31.41
1998	32.32
1999	33.36
2000	34.52
2001	36.19
2002	38.04
2003	39.91
2004	41.9
2005	44.1
2006	45.26
2007	46.56
2008	47.95
2009	49.39
2010	50.94
2011	52.68
2012	54.53
2013	56.18
2014	58.21
2015	60.35
2016	62.62