Year	mmol per litre
1980	5.641
1981	5.618
1982	5.591
1983	5.568
1984	5.545
1985	5.524
1986	5.502
1987	5.48
1988	5.464
1989	5.45
1990	5.434
1991	5.414
1992	5.393
1993	5.371
1994	5.352
1995	5.334
1996	5.313
1997	5.29
1998	5.272
1999	5.255
2000	5.239
2001	5.225
2002	5.211
2003	5.193
2004	5.178
2005	5.158
2006	5.139
2007	5.116
2008	5.094