Year	Number of
1990	50.13
1991	48.7
1992	48.18
1993	47.35
1994	47.4
1995	46.24
1996	45.17
1997	43.57
1998	42.27
1999	40.95
2000	40.9
2001	41.76
2002	41.65
2003	42.11
2004	43.39
2005	44.12
2006	44.2
2007	44.94
2008	46.07
2009	47.5
2010	48.59
2011	50.06
2012	51.72
2013	53.48
2014	55.13
2015	57.03
2016	59.28