Year	Number of
1990	62.73
1991	62.35
1992	61.53
1993	60.69
1994	60.2
1995	60.53
1996	61.68
1997	63.95
1998	66.92
1999	69.7
2000	72.53
2001	74.92
2002	77.54
2003	80.51
2004	83.77
2005	87.48
2006	91.17
2007	95.22
2008	99.98
2009	105.18
2010	110.97
2011	116.31
2012	122.04
2013	128.04
2014	134.29
2015	140.72
2016	146.27