Year	Number of
1990	40.17
1991	40.32
1992	40.13
1993	39.68
1994	39.17
1995	38.73
1996	39.13
1997	39.66
1998	40.47
1999	41.59
2000	43.08
2001	45.44
2002	48.41
2003	51.91
2004	55.57
2005	59.27
2006	61.94
2007	64.33
2008	66.63
2009	68.99
2010	71.59
2011	73.34
2012	75.23
2013	77.13
2014	79.09
2015	81.12
2016	83.71