Year	Number of
1990	35.33
1991	36.93
1992	38.55
1993	40.27
1994	42.12
1995	44.31
1996	45.37
1997	45.53
1998	45.36
1999	45.25
2000	45.53
2001	46.53
2002	48.24
2003	49.57
2004	50.51
2005	51.2
2006	51.81
2007	51.96
2008	52.27
2009	53.29
2010	54.69
2011	56.36
2012	57.8
2013	59.13
2014	60.62
2015	63.74
2016	67.17