Year	mmol per litre
1980	5.845
1981	5.827
1982	5.807
1983	5.789
1984	5.769
1985	5.752
1986	5.734
1987	5.715
1988	5.692
1989	5.669
1990	5.647
1991	5.627
1992	5.606
1993	5.583
1994	5.564
1995	5.545
1996	5.524
1997	5.503
1998	5.479
1999	5.456
2000	5.429
2001	5.405
2002	5.382
2003	5.358
2004	5.334
2005	5.315
2006	5.298
2007	5.285
2008	5.273