Year	Number of
1990	220.16
1991	223.55
1992	228.89
1993	239.19
1994	248.13
1995	260.8
1996	264.16
1997	273.16
1998	281.15
1999	281.03
2000	291.7
2001	302.1
2002	309.6
2003	317.83
2004	337.28
2005	359.9
2006	372.18
2007	382.88
2008	400.26
2009	433.9
2010	453.28
2011	484.67
2012	513.58
2013	548.49
2014	576.06
2015	608.87
2016	641.51