Year	mmol per litre
1980	5.95
1981	5.927
1982	5.904
1983	5.879
1984	5.858
1985	5.838
1986	5.815
1987	5.788
1988	5.759
1989	5.729
1990	5.696
1991	5.669
1992	5.64
1993	5.613
1994	5.589
1995	5.564
1996	5.542
1997	5.52
1998	5.498
1999	5.474
2000	5.452
2001	5.431
2002	5.41
2003	5.389
2004	5.373
2005	5.358
2006	5.346
2007	5.334
2008	5.322