Year	Number of
1990	37.4
1991	38.82
1992	40.86
1993	42.72
1994	44.58
1995	46.3
1996	47.54
1997	49.05
1998	50.92
1999	52.89
2000	54.27
2001	55.16
2002	55.84
2003	57.3
2004	58.57
2005	59.43
2006	59.48
2007	59.27
2008	58.64
2009	58.48
2010	59.84
2011	61.29
2012	62.32
2013	63.43
2014	64.68
2015	65.9
2016	67.38