Year	Number of
1990	40.9
1991	43
1992	45.12
1993	47.54
1994	50.12
1995	51.37
1996	51.44
1997	54.17
1998	54.85
1999	55.79
2000	57.52
2001	59.85
2002	60.93
2003	62.15
2004	63.57
2005	64.11
2006	65.96
2007	68.16
2008	71.34
2009	75.34
2010	79.31
2011	83.17
2012	87.18
2013	91.61
2014	95.5
2015	98.8
2016	102.44