Year	mmol per litre
1980	5.62
1981	5.603
1982	5.585
1983	5.568
1984	5.552
1985	5.533
1986	5.517
1987	5.503
1988	5.491
1989	5.478
1990	5.466
1991	5.453
1992	5.438
1993	5.426
1994	5.414
1995	5.405
1996	5.391
1997	5.375
1998	5.363
1999	5.351
2000	5.338
2001	5.326
2002	5.314
2003	5.301
2004	5.286
2005	5.27
2006	5.254
2007	5.241
2008	5.225