Year	Number of
1990	23.49
1991	23.97
1992	24.52
1993	25.14
1994	25.81
1995	26.49
1996	27.57
1997	28.73
1998	30.1
1999	31.64
2000	33.5
2001	35.68
2002	38.2
2003	41.14
2004	44.23
2005	47.86
2006	47.65
2007	47.5
2008	47.56
2009	47.43
2010	47.52
2011	48.29
2012	49.25
2013	50.21
2014	51.14
2015	52.07
2016	53.06