Year	mmol per litre
1980	4.572
1981	4.548
1982	4.523
1983	4.498
1984	4.476
1985	4.456
1986	4.437
1987	4.419
1988	4.4
1989	4.38
1990	4.36
1991	4.336
1992	4.309
1993	4.278
1994	4.247
1995	4.221
1996	4.196
1997	4.173
1998	4.152
1999	4.13
2000	4.109
2001	4.089
2002	4.071
2003	4.058
2004	4.045
2005	4.035
2006	4.025
2007	4.017
2008	4.011