Year	mmol per litre
1980	5.705
1981	5.693
1982	5.681
1983	5.668
1984	5.656
1985	5.64
1986	5.625
1987	5.614
1988	5.602
1989	5.593
1990	5.583
1991	5.572
1992	5.554
1993	5.526
1994	5.493
1995	5.457
1996	5.423
1997	5.389
1998	5.364
1999	5.349
2000	5.326
2001	5.307
2002	5.297
2003	5.287
2004	5.282
2005	5.272
2006	5.261
2007	5.248
2008	5.232