Year	Number of
1990	34.73
1991	36.64
1992	38.56
1993	40.22
1994	41.61
1995	43.53
1996	45.23
1997	45.96
1998	45.71
1999	44.96
2000	43.74
2001	43.11
2002	43.04
2003	43.5
2004	44.04
2005	44.5
2006	45.02
2007	45.29
2008	46.05
2009	47.63
2010	49.52
2011	50.32
2012	51.19
2013	52.3
2014	53.14
2015	55
2016	57.09