Year	mm Hg
1980	137.2
1981	137
1982	136.8
1983	136.5
1984	136.1
1985	135.7
1986	135.3
1987	134.8
1988	134.4
1989	134.1
1990	133.7
1991	133.3
1992	132.9
1993	132.6
1994	132.3
1995	132
1996	131.8
1997	131.7
1998	131.6
1999	131.5
2000	131.4
2001	131.4
2002	131.3
2003	131.3
2004	131.4
2005	131.6
2006	131.8
2007	132
2008	132.2