Year	Number of
1990	23.05
1991	24.05
1992	25.11
1993	26.33
1994	27.7
1995	29.21
1996	30.79
1997	32.51
1998	34.91
1999	37.84
2000	41.48
2001	43.78
2002	46.99
2003	50.49
2004	55.16
2005	59.02
2006	61.47
2007	64.66
2008	66.17
2009	68.83
2010	72.12
2011	74.9
2012	76.8
2013	80.4
2014	83.54
2015	87.18
2016	91.46