Year	Kg per Square Metre
1980	27.17
1981	27.45
1982	27.74
1983	28.01
1984	28.3
1985	28.59
1986	28.87
1987	29.15
1988	29.42
1989	29.68
1990	29.95
1991	30.21
1992	30.46
1993	30.71
1994	30.95
1995	31.2
1996	31.46
1997	31.7
1998	31.93
1999	32.16
2000	32.42
2001	32.67
2002	32.91
2003	33.13
2004	33.35
2005	33.58
2006	33.8
2007	34.03
2008	34.26