Year	mmol per litre
1980	5.953
1981	5.928
1982	5.902
1983	5.881
1984	5.86
1985	5.842
1986	5.822
1987	5.804
1988	5.784
1989	5.766
1990	5.746
1991	5.725
1992	5.701
1993	5.675
1994	5.646
1995	5.618
1996	5.586
1997	5.554
1998	5.523
1999	5.492
2000	5.462
2001	5.437
2002	5.413
2003	5.39
2004	5.367
2005	5.347
2006	5.328
2007	5.309
2008	5.291