Year	Number of
1990	39.81
1991	39.75
1992	38.3
1993	36.66
1994	35.43
1995	35.13
1996	37.13
1997	40.19
1998	45.53
1999	50.08
2000	53.47
2001	55.24
2002	56.66
2003	57.26
2004	58.71
2005	61.15
2006	65.61
2007	69.75
2008	73.79
2009	77.47
2010	80.62
2011	83.95
2012	87.36
2013	92.23
2014	97.91
2015	104.61
2016	111.42