Year	Number of
1990	38.35
1991	38.84
1992	39.11
1993	39.73
1994	41.34
1995	42.45
1996	44.46
1997	45.54
1998	46.97
1999	48.17
2000	49.18
2001	50.8
2002	50.78
2003	52.34
2004	53.52
2005	53.25
2006	54.23
2007	53.74
2008	54.75
2009	55.12
2010	54.5
2011	55.28
2012	55.42
2013	55.22
2014	55.8
2015	56.59
2016	57.29