Year	mmol per litre
1980	4.644
1981	4.637
1982	4.631
1983	4.625
1984	4.62
1985	4.613
1986	4.608
1987	4.598
1988	4.583
1989	4.568
1990	4.548
1991	4.531
1992	4.509
1993	4.481
1994	4.452
1995	4.426
1996	4.403
1997	4.385
1998	4.371
1999	4.356
2000	4.334
2001	4.31
2002	4.295
2003	4.284
2004	4.272
2005	4.262
2006	4.253
2007	4.246
2008	4.239