Year	Kg per Square Metre
1980	25.93
1981	26.02
1982	26.13
1983	26.24
1984	26.37
1985	26.5
1986	26.65
1987	26.8
1988	26.97
1989	27.13
1990	27.32
1991	27.51
1992	27.7
1993	27.91
1994	28.13
1995	28.34
1996	28.57
1997	28.81
1998	29.07
1999	29.33
2000	29.58
2001	29.82
2002	30.05
2003	30.28
2004	30.49
2005	30.7
2006	30.91
2007	31.11
2008	31.31