Year	Number of
1990	38.18
1991	37.7
1992	36.94
1993	36.01
1994	35.09
1995	34.28
1996	35.09
1997	36.09
1998	37.39
1999	38.87
2000	40.49
2001	42.69
2002	45.09
2003	47.67
2004	50.26
2005	52.82
2006	54.94
2007	56.9
2008	58.77
2009	60.63
2010	62.55
2011	64.98
2012	67.54
2013	70.22
2014	73.02
2015	75.94
2016	79.51