Year	Number of
1990	38.84
1991	39.89
1992	40.77
1993	42.94
1994	43.14
1995	44.67
1996	45.87
1997	47.28
1998	48.71
1999	49.86
2000	51
2001	51.31
2002	51.89
2003	52.59
2004	53.67
2005	54.19
2006	54.35
2007	55.27
2008	55.4
2009	57.33
2010	59.03
2011	61.03
2012	61.84
2013	61.65
2014	64.06
2015	66.33
2016	68.14