Year	mmol per litre
1980	4.625
1981	4.605
1982	4.582
1983	4.557
1984	4.533
1985	4.508
1986	4.485
1987	4.462
1988	4.441
1989	4.42
1990	4.399
1991	4.378
1992	4.357
1993	4.33
1994	4.309
1995	4.29
1996	4.272
1997	4.254
1998	4.238
1999	4.222
2000	4.205
2001	4.188
2002	4.17
2003	4.155
2004	4.138
2005	4.121
2006	4.105
2007	4.09
2008	4.074