Year	Number of
1990	67.55
1991	71.22
1992	75.78
1993	80.79
1994	87.01
1995	94.15
1996	100.24
1997	106.43
1998	113.18
1999	120.08
2000	127.45
2001	127.62
2002	127.72
2003	126.54
2004	124.53
2005	122.33
2006	123.54
2007	124.61
2008	126.38
2009	127.86
2010	130.15
2011	131.2
2012	133.15
2013	135.57
2014	137.24
2015	140.23
2016	143.55