Year	Kg per Square Metre
1980	25.26
1981	25.34
1982	25.41
1983	25.48
1984	25.56
1985	25.64
1986	25.73
1987	25.82
1988	25.92
1989	26
1990	26.09
1991	26.17
1992	26.26
1993	26.35
1994	26.46
1995	26.58
1996	26.7
1997	26.82
1998	26.94
1999	27.07
2000	27.2
2001	27.32
2002	27.44
2003	27.56
2004	27.69
2005	27.82
2006	27.95
2007	28.09
2008	28.23