Year	Number of
1990	37.18
1991	37.05
1992	36.73
1993	36.29
1994	35.85
1995	35.56
1996	35.98
1997	36.63
1998	37.52
1999	38.57
2000	39.79
2001	41.29
2002	42.97
2003	44.8
2004	46.67
2005	48.59
2006	50.11
2007	51.54
2008	52.96
2009	54.37
2010	55.86
2011	57.14
2012	58.54
2013	60.01
2014	61.55
2015	63.15
2016	65.01