Year	mmol per litre
1980	6.089
1981	6.063
1982	6.035
1983	6.007
1984	5.978
1985	5.948
1986	5.918
1987	5.887
1988	5.853
1989	5.817
1990	5.776
1991	5.732
1992	5.685
1993	5.637
1994	5.59
1995	5.541
1996	5.49
1997	5.438
1998	5.386
1999	5.334
2000	5.283
2001	5.233
2002	5.185
2003	5.141
2004	5.098
2005	5.061
2006	5.025
2007	4.99
2008	4.958