Year	Number of
1990	57.98
1991	60.19
1992	62.55
1993	65.17
1994	67.92
1995	70.85
1996	74.42
1997	78.24
1998	82.6
1999	87.16
2000	91.99
2001	95.28
2002	98.72
2003	102.64
2004	106.73
2005	111.12
2006	115.06
2007	119.12
2008	123.51
2009	128.15
2010	133.15
2011	137.68
2012	142.63
2013	147.89
2014	153.44
2015	159.27
2016	165.4