Year	Number of
1990	41.39
1991	41.58
1992	41.81
1993	41.91
1994	42.02
1995	42.17
1996	42.61
1997	43.13
1998	43.66
1999	44.22
2000	44.87
2001	44.98
2002	45.25
2003	45.63
2004	46.03
2005	46.44
2006	46.49
2007	46.48
2008	46.63
2009	46.82
2010	47.11
2011	48.06
2012	49.15
2013	50.32
2014	51.55
2015	52.81
2016	54.11