Year	mmol per litre
1980	6.134
1981	6.106
1982	6.075
1983	6.045
1984	6.022
1985	5.994
1986	5.968
1987	5.937
1988	5.903
1989	5.868
1990	5.831
1991	5.79
1992	5.745
1993	5.703
1994	5.657
1995	5.617
1996	5.576
1997	5.538
1998	5.494
1999	5.454
2000	5.416
2001	5.385
2002	5.354
2003	5.33
2004	5.302
2005	5.275
2006	5.247
2007	5.221
2008	5.193