Year	Kg per Square Metre
1980	27.42
1981	27.56
1982	27.7
1983	27.84
1984	28
1985	28.15
1986	28.3
1987	28.43
1988	28.55
1989	28.67
1990	28.77
1991	28.86
1992	28.97
1993	29.07
1994	29.16
1995	29.26
1996	29.34
1997	29.42
1998	29.5
1999	29.55
2000	29.61
2001	29.68
2002	29.76
2003	29.83
2004	29.9
2005	29.98
2006	30.09
2007	30.2
2008	30.32