Year	Kg per Square Metre
1980	28.12
1981	28.36
1982	28.58
1983	28.82
1984	29.05
1985	29.28
1986	29.52
1987	29.75
1988	29.98
1989	30.2
1990	30.42
1991	30.64
1992	30.85
1993	31.04
1994	31.23
1995	31.41
1996	31.59
1997	31.77
1998	31.95
1999	32.13
2000	32.32
2001	32.51
2002	32.7
2003	32.9
2004	33.1
2005	33.3
2006	33.49
2007	33.69
2008	33.9