Year	mmol per litre
1980	5.857
1981	5.84
1982	5.817
1983	5.8
1984	5.782
1985	5.769
1986	5.753
1987	5.736
1988	5.714
1989	5.692
1990	5.671
1991	5.652
1992	5.633
1993	5.609
1994	5.593
1995	5.578
1996	5.562
1997	5.545
1998	5.526
1999	5.506
2000	5.481
2001	5.458
2002	5.437
2003	5.412
2004	5.381
2005	5.358
2006	5.335
2007	5.315
2008	5.297