Year	mmol per litre
1980	5.288
1981	5.286
1982	5.284
1983	5.282
1984	5.28
1985	5.277
1986	5.276
1987	5.278
1988	5.28
1989	5.284
1990	5.285
1991	5.277
1992	5.268
1993	5.258
1994	5.249
1995	5.235
1996	5.223
1997	5.212
1998	5.204
1999	5.2
2000	5.195
2001	5.191
2002	5.19
2003	5.185
2004	5.183
2005	5.181
2006	5.179
2007	5.177
2008	5.175