Year	mmol per litre
1980	5.659
1981	5.655
1982	5.647
1983	5.629
1984	5.603
1985	5.57
1986	5.523
1987	5.484
1988	5.449
1989	5.412
1990	5.387
1991	5.368
1992	5.347
1993	5.33
1994	5.316
1995	5.304
1996	5.306
1997	5.303
1998	5.293
1999	5.283
2000	5.273
2001	5.258
2002	5.246
2003	5.24
2004	5.227
2005	5.214
2006	5.201
2007	5.189
2008	5.179