Year	Kg per Square Metre
1980	26.3
1981	26.41
1982	26.53
1983	26.66
1984	26.81
1985	26.97
1986	27.13
1987	27.28
1988	27.49
1989	27.7
1990	27.94
1991	28.17
1992	28.4
1993	28.61
1994	28.82
1995	29.05
1996	29.28
1997	29.51
1998	29.73
1999	29.94
2000	30.12
2001	30.33
2002	30.53
2003	30.74
2004	30.94
2005	31.16
2006	31.38
2007	31.61
2008	31.85