Year	mmol per litre
1980	4.62
1981	4.6
1982	4.579
1983	4.556
1984	4.531
1985	4.506
1986	4.485
1987	4.464
1988	4.444
1989	4.427
1990	4.412
1991	4.394
1992	4.378
1993	4.36
1994	4.343
1995	4.326
1996	4.311
1997	4.296
1998	4.284
1999	4.271
2000	4.261
2001	4.25
2002	4.239
2003	4.227
2004	4.216
2005	4.205
2006	4.193
2007	4.182
2008	4.171