Year	Number of
1990	39.35
1991	39.13
1992	38.3
1993	37.34
1994	36.69
1995	37
1996	38.68
1997	41.23
1998	45.09
1999	48.17
2000	50.33
2001	51.2
2002	51.81
2003	51.87
2004	52.52
2005	54.03
2006	56.71
2007	59.64
2008	62.52
2009	65.08
2010	67.45
2011	70.25
2012	73.35
2013	77.12
2014	81.49
2015	86.57
2016	91.71