Year	Number of
1990	51.62
1991	53.38
1992	55.11
1993	56.63
1994	58.15
1995	59.91
1996	61.7
1997	63.49
1998	65.29
1999	67.13
2000	69
2001	71.69
2002	74.76
2003	77.51
2004	80.68
2005	83.98
2006	87.39
2007	90.75
2008	94.1
2009	97.75
2010	101.46
2011	105.39
2012	109.25
2013	112.77
2014	116.64
2015	120.6
2016	125.13