Year	Number of
1990	179.63
1991	181.14
1992	179.23
1993	175.25
1994	170.7
1995	166.44
1996	164.69
1997	165.34
1998	168.88
1999	166.89
2000	175.89
2001	175.6
2002	169.33
2003	168.59
2004	171.24
2005	163.42
2006	159.32
2007	165.29
2008	179.76
2009	192.9
2010	200.07
2011	210.04
2012	223.95
2013	225.16
2014	235.58
2015	227.31
2016	226.45