Year	Number of
1990	146.23
1991	149.3
1992	151.97
1993	154.38
1994	157.24
1995	160.87
1996	157.2
1997	153.93
1998	150.76
1999	147.17
2000	143.19
2001	144.15
2002	144.33
2003	144.52
2004	143.96
2005	142.95
2006	139.59
2007	136.6
2008	133.52
2009	131.12
2010	129.39
2011	132.08
2012	134.87
2013	137.67
2014	140.33
2015	143.11
2016	145.78