Year	Number of
1990	36.13
1991	36.92
1992	37.76
1993	38.66
1994	39.63
1995	40.72
1996	40.92
1997	41.22
1998	41.58
1999	42.02
2000	42.57
2001	42.24
2002	42.02
2003	41.85
2004	41.76
2005	41.79
2006	42.16
2007	42.57
2008	43.11
2009	43.75
2010	44.54
2011	45.17
2012	45.93
2013	46.77
2014	47.71
2015	48.77
2016	49.77