Year	Number of
1990	23.23
1991	23.72
1992	24.82
1993	25.48
1994	27.05
1995	27.73
1996	28.8
1997	30.49
1998	32.1
1999	33.44
2000	34.62
2001	35.75
2002	37.34
2003	38.5
2004	40.22
2005	41.38
2006	42.79
2007	43.83
2008	44.37
2009	44.64
2010	45.19
2011	46.1
2012	47.05
2013	47.8
2014	48.2
2015	48.2
2016	48.67