Year	Number of
1990	137.03
1991	141.38
1992	147.27
1993	153.37
1994	161.29
1995	168.3
1996	174.95
1997	180.51
1998	185.11
1999	181.91
2000	180.18
2001	179.74
2002	179.01
2003	179.41
2004	182.8
2005	185.4
2006	186.99
2007	190.8
2008	195.42
2009	201.36
2010	207.82
2011	213.51
2012	220.78
2013	228.55
2014	236.44
2015	244.88
2016	253.59