Year	years
1970	7
1971	7
1972	7
1973	7
1974	7
1975	7
1976	7
1977	7
1978	7
1979	7
1980	7
1981	7
1982	7
1983	7
1984	7
1985	7
1986	7
1987	7
1988	7
1989	7
1990	7
1991	7
1992	7
1993	7
1994	7
1995	7
1996	7
1997	7
1998	7
1999	7
2000	7
2001	7
2002	7
2003	6.5
2004	6.5
2005	6.5
2006	6.5
2007	6
2008	6
2009	6
2010	6
2011	6
2012	6.5
2013	6.5
2014	6.5
2015	6.5
2016	6.5
2017	6.5
2018	6.5
2019	6.5
2020	6.5
2021	6.5
2022	6.5
2023	6.5