Year	mmol per litre
1980	4.808
1981	4.791
1982	4.773
1983	4.754
1984	4.736
1985	4.718
1986	4.7
1987	4.678
1988	4.658
1989	4.637
1990	4.616
1991	4.594
1992	4.57
1993	4.545
1994	4.519
1995	4.496
1996	4.473
1997	4.451
1998	4.431
1999	4.414
2000	4.4
2001	4.387
2002	4.373
2003	4.358
2004	4.342
2005	4.324
2006	4.308
2007	4.291
2008	4.274