Year	Number of
1990	22.99
1991	24.9
1992	25.82
1993	27.83
1994	30.57
1995	32.86
1996	33.02
1997	36.55
1998	37.73
1999	41.13
2000	42.4
2001	45.45
2002	47.85
2003	51.49
2004	55.08
2005	56.66
2006	60.87
2007	63.66
2008	66.55
2009	69.04
2010	70.12
2011	70.3
2012	72.9
2013	76.96
2014	79.94
2015	80.87
2016	83.16