Year	Number of
1990	180.54
1991	178.3
1992	175.63
1993	172.79
1994	170.77
1995	169.82
1996	165.95
1997	162.66
1998	159.78
1999	156.57
2000	152.89
2001	152.38
2002	151.33
2003	150.72
2004	150.12
2005	149.87
2006	147.36
2007	145.4
2008	143.38
2009	142
2010	141.24
2011	143.22
2012	145.31
2013	147.5
2014	149.46
2015	151.38
2016	153.47