Year	Kg per Square Metre
1980	26.29
1981	26.5
1982	26.71
1983	26.92
1984	27.14
1985	27.37
1986	27.59
1987	27.81
1988	27.99
1989	28.22
1990	28.44
1991	28.63
1992	28.81
1993	29
1994	29.22
1995	29.4
1996	29.62
1997	29.83
1998	30.04
1999	30.22
2000	30.44
2001	30.65
2002	30.87
2003	31.08
2004	31.28
2005	31.48
2006	31.67
2007	31.87
2008	32.07