Year	Number of
1990	38.44
1991	40.1
1992	41.8
1993	43.44
1994	44.84
1995	45.9
1996	45.75
1997	44.98
1998	43.86
1999	42.77
2000	41.94
2001	41.81
2002	42.35
2003	43.26
2004	44.14
2005	44.79
2006	46.54
2007	48.07
2008	49.51
2009	50.92
2010	52.45
2011	55
2012	57.55
2013	60.15
2014	63.08
2015	66.43
2016	69.67