Year	Number of
1990	226.42
1991	231.57
1992	236.79
1993	242.1
1994	247.71
1995	253.96
1996	254.79
1997	256.33
1998	258.3
1999	260.7
2000	263.67
2001	262.86
2002	262.61
2003	262.71
2004	263.17
2005	264.14
2006	267.86
2007	271.76
2008	276.27
2009	281.12
2010	286.56
2011	293.24
2012	300.58
2013	308.28
2014	316.42
2015	324.98
2016	334.07