Year	Number of
1990	96.54
1991	98.35
1992	99.9
1993	101.16
1994	101.82
1995	106.7
1996	111.36
1997	115.87
1998	121.35
1999	125.23
2000	127.65
2001	130.08
2002	133.18
2003	136.19
2004	139.91
2005	140.62
2006	140.03
2007	138.76
2008	138.36
2009	138.91
2010	138.53
2011	136.53
2012	135.96
2013	136.61
2014	137.71
2015	138.92
2016	139.87