Year	Number of
1990	34.27
1991	34.45
1992	34.67
1993	34.99
1994	35.32
1995	35.68
1996	35.86
1997	36.06
1998	36.32
1999	36.62
2000	36.97
2001	38.88
2002	40.97
2003	43.32
2004	45.82
2005	48.49
2006	50.08
2007	51.68
2008	53.51
2009	55.4
2010	57.41
2011	60.02
2012	62.83
2013	65.92
2014	69.18
2015	72.6
2016	76.11