Year	Number of
1990	43.28
1991	43.15
1992	42.84
1993	41.93
1994	41.8
1995	41.87
1996	41.95
1997	43.54
1998	43.15
1999	44.08
2000	44.79
2001	47.29
2002	51.43
2003	54.35
2004	57.74
2005	60.72
2006	63.64
2007	67.34
2008	69.81
2009	72.71
2010	75.68
2011	78.5
2012	81.06
2013	83.22
2014	85.59
2015	88.51
2016	92.63