Year	Number of
1990	311.86
1991	307.42
1992	304.87
1993	299.62
1994	294.09
1995	291.36
1996	280.92
1997	274.78
1998	270.83
1999	267.28
2000	269.85
2001	274.16
2002	282.43
2003	291.75
2004	299.09
2005	305.36
2006	310.09
2007	312.34
2008	312.07
2009	311.48
2010	311.57
2011	310.94
2012	310.68
2013	311.2
2014	312.67
2015	309.54
2016	306.79