Year	Kg per Square Metre
1980	28.28
1981	28.57
1982	28.85
1983	29.14
1984	29.42
1985	29.71
1986	29.99
1987	30.27
1988	30.52
1989	30.78
1990	31.03
1991	31.26
1992	31.5
1993	31.71
1994	31.92
1995	32.12
1996	32.32
1997	32.52
1998	32.73
1999	32.95
2000	33.16
2001	33.38
2002	33.61
2003	33.84
2004	34.08
2005	34.32
2006	34.55
2007	34.79
2008	35.02