Year	mmol per litre
1980	5.662
1981	5.665
1982	5.663
1983	5.65
1984	5.635
1985	5.612
1986	5.576
1987	5.547
1988	5.516
1989	5.488
1990	5.468
1991	5.452
1992	5.437
1993	5.423
1994	5.415
1995	5.408
1996	5.41
1997	5.408
1998	5.399
1999	5.389
2000	5.379
2001	5.363
2002	5.35
2003	5.343
2004	5.329
2005	5.313
2006	5.302
2007	5.29
2008	5.281