Year	mmol per litre
1980	4.649
1981	4.634
1982	4.62
1983	4.605
1984	4.588
1985	4.573
1986	4.556
1987	4.538
1988	4.52
1989	4.496
1990	4.472
1991	4.449
1992	4.426
1993	4.406
1994	4.388
1995	4.37
1996	4.354
1997	4.341
1998	4.331
1999	4.321
2000	4.312
2001	4.305
2002	4.297
2003	4.29
2004	4.281
2005	4.271
2006	4.26
2007	4.249
2008	4.238