Year	Number of
1990	131.34
1991	133.74
1992	133.04
1993	132.35
1994	132.86
1995	132.35
1996	133.68
1997	134.46
1998	135.49
1999	136.71
2000	138.52
2001	138.83
2002	138.27
2003	138.97
2004	139.73
2005	139.98
2006	141.22
2007	141.74
2008	140.67
2009	141.13
2010	141.02
2011	140.15
2012	140.61
2013	140.21
2014	139.34
2015	138.19
2016	137.14