Year	Number of
1990	35.23
1991	37.47
1992	39.88
1993	42.57
1994	45.42
1995	48.43
1996	50.63
1997	52.89
1998	55.4
1999	57.98
2000	60.67
2001	65.52
2002	70.74
2003	76.51
2004	82.72
2005	89.43
2006	94.53
2007	99.86
2008	105.58
2009	111.67
2010	118.23
2011	125.08
2012	132.5
2013	140.5
2014	148.96
2015	157.88
2016	167.47