Year	Number of
1990	100.42
1991	108.75
1992	117.64
1993	125.63
1994	137.56
1995	149.77
1996	159.62
1997	167.4
1998	175.88
1999	179.74
2000	180.72
2001	181.17
2002	179.07
2003	179.4
2004	172.67
2005	168.86
2006	166.05
2007	162.26
2008	157.21
2009	154.33
2010	151.76
2011	148.63
2012	145.68
2013	143
2014	140.23
2015	139.18
2016	139.48