Year	Number of
1990	55.83
1991	57.24
1992	58.98
1993	58.33
1994	60.51
1995	64.93
1996	66.22
1997	65.71
1998	65.3
1999	69.42
2000	71.51
2001	75.08
2002	77.04
2003	81.77
2004	85.34
2005	85.9
2006	85.6
2007	88.31
2008	92.37
2009	96.12
2010	101.98
2011	103.34
2012	105.44
2013	107.31
2014	109.49
2015	111.62
2016	114.34