Year	Kg per Square Metre
1980	27.54
1981	27.67
1982	27.79
1983	27.92
1984	28.05
1985	28.18
1986	28.31
1987	28.41
1988	28.5
1989	28.54
1990	28.59
1991	28.63
1992	28.68
1993	28.73
1994	28.79
1995	28.85
1996	28.9
1997	28.95
1998	28.99
1999	29.02
2000	29.05
2001	29.07
2002	29.11
2003	29.13
2004	29.15
2005	29.17
2006	29.19
2007	29.2
2008	29.22