Year	mmol per litre
1980	6.127
1981	6.09
1982	6.048
1983	6.004
1984	5.956
1985	5.911
1986	5.861
1987	5.813
1988	5.766
1989	5.724
1990	5.677
1991	5.641
1992	5.607
1993	5.572
1994	5.537
1995	5.507
1996	5.477
1997	5.452
1998	5.428
1999	5.408
2000	5.385
2001	5.365
2002	5.341
2003	5.322
2004	5.303
2005	5.283
2006	5.268
2007	5.254
2008	5.241