Year	mmol per litre
1980	4.465
1981	4.453
1982	4.441
1983	4.43
1984	4.413
1985	4.398
1986	4.384
1987	4.367
1988	4.351
1989	4.34
1990	4.329
1991	4.32
1992	4.306
1993	4.291
1994	4.279
1995	4.266
1996	4.257
1997	4.25
1998	4.246
1999	4.241
2000	4.237
2001	4.232
2002	4.222
2003	4.208
2004	4.194
2005	4.179
2006	4.163
2007	4.147
2008	4.133