Year	Number of
1990	51.38
1991	52.06
1992	51.4
1993	52.48
1994	53.14
1995	54.95
1996	57.02
1997	58.29
1998	57.7
1999	57.69
2000	58.14
2001	57.53
2002	57.57
2003	58.48
2004	59.15
2005	60.82
2006	61.73
2007	62.73
2008	62.55
2009	63.56
2010	64
2011	64.4
2012	65.38
2013	66.48
2014	67.17
2015	67.79
2016	71.23