Year	Number of
1990	37.08
1991	38.55
1992	39.96
1993	41.34
1994	42.9
1995	44.43
1996	46.02
1997	47.47
1998	48.82
1999	49.91
2000	50.89
2001	51.7
2002	52.72
2003	54.14
2004	55.64
2005	56.95
2006	58.15
2007	59.88
2008	61.55
2009	62.91
2010	64.08
2011	65.16
2012	66.49
2013	67.96
2014	69.5
2015	71.04
2016	72.54