Year	mmol per litre
1980	5.923
1981	5.899
1982	5.872
1983	5.844
1984	5.813
1985	5.786
1986	5.757
1987	5.73
1988	5.703
1989	5.681
1990	5.653
1991	5.634
1992	5.616
1993	5.595
1994	5.571
1995	5.551
1996	5.531
1997	5.515
1998	5.498
1999	5.483
2000	5.464
2001	5.446
2002	5.424
2003	5.405
2004	5.384
2005	5.359
2006	5.339
2007	5.319
2008	5.299