Year	Number of
1990	52.23
1991	54.3
1992	55.05
1993	56.92
1994	58.53
1995	60.31
1996	62.1
1997	64.12
1998	66.33
1999	68.54
2000	70.99
2001	73.86
2002	72.8
2003	76.72
2004	80.3
2005	83.81
2006	86.1
2007	89.99
2008	94.67
2009	102.74
2010	108.73
2011	114.16
2012	115.53
2013	116.55
2014	122.72
2015	128
2016	132.63