Year	Number of
1990	163.56
1991	163.72
1992	170.83
1993	167.21
1994	160.28
1995	172.47
1996	179.71
1997	182.55
1998	191.05
1999	193.26
2000	194.45
2001	195.89
2002	196.08
2003	206.5
2004	210.32
2005	223.57
2006	234.79
2007	231.94
2008	240.27
2009	242.54
2010	248.97
2011	255.71
2012	260.18
2013	259.49
2014	260.31
2015	271.98
2016	268.85