Year	Number of
1990	35.65
1991	35.42
1992	34.97
1993	34.51
1994	34.29
1995	34.46
1996	35.32
1997	36.77
1998	38.74
1999	40.6
2000	42.45
2001	43.88
2002	45.37
2003	47.05
2004	48.9
2005	51.02
2006	53.39
2007	56.02
2008	59.04
2009	62.33
2010	65.9
2011	68.73
2012	71.8
2013	75.02
2014	78.3
2015	81.57
2016	84.37