Year	Number of
1990	53.83
1991	56.65
1992	61.15
1993	65.61
1994	71.09
1995	72.33
1996	76.8
1997	81.14
1998	86.43
1999	91.23
2000	95.85
2001	100.18
2002	106.78
2003	117.26
2004	130.42
2005	146.26
2006	164.05
2007	169.59
2008	180.17
2009	189.55
2010	198.26
2011	210.86
2012	218.21
2013	218.16
2014	225.62
2015	231.06
2016	223.41