Year	mmol per litre
1980	5.772
1981	5.759
1982	5.744
1983	5.731
1984	5.712
1985	5.697
1986	5.678
1987	5.658
1988	5.643
1989	5.626
1990	5.605
1991	5.583
1992	5.563
1993	5.546
1994	5.527
1995	5.505
1996	5.488
1997	5.476
1998	5.465
1999	5.452
2000	5.442
2001	5.434
2002	5.427
2003	5.418
2004	5.409
2005	5.405
2006	5.405
2007	5.408
2008	5.41