Year	mmol per litre
1980	5.965
1981	5.946
1982	5.922
1983	5.897
1984	5.873
1985	5.848
1986	5.823
1987	5.799
1988	5.775
1989	5.75
1990	5.722
1991	5.696
1992	5.671
1993	5.644
1994	5.618
1995	5.592
1996	5.567
1997	5.543
1998	5.52
1999	5.499
2000	5.478
2001	5.457
2002	5.437
2003	5.418
2004	5.399
2005	5.379
2006	5.359
2007	5.344
2008	5.328