Year	Number of
1990	38.96
1991	39.46
1992	40.04
1993	39.71
1994	41.75
1995	42.3
1996	41.15
1997	41.64
1998	41.56
1999	43.26
2000	45.29
2001	45.95
2002	48.46
2003	50.82
2004	53.3
2005	55.81
2006	56.41
2007	57.25
2008	59.89
2009	60.25
2010	61.29
2011	62.15
2012	61.04
2013	61.83
2014	65.48
2015	66.96
2016	68.45