Year	Number of
1990	38.75
1991	39.1
1992	39.42
1993	39.93
1994	40.36
1995	40.55
1996	40.03
1997	39.51
1998	39.75
1999	40.42
2000	41.45
2001	42.39
2002	43.68
2003	45.48
2004	47.36
2005	49.14
2006	50.14
2007	50.77
2008	51.89
2009	52.99
2010	54.08
2011	53.77
2012	53.08
2013	52.62
2014	52.2
2015	52.03
2016	52.16