Year	mm Hg
1980	136.6
1981	136.3
1982	136
1983	135.7
1984	135.5
1985	135.2
1986	134.9
1987	134.7
1988	134.4
1989	134.1
1990	133.8
1991	133.5
1992	133.1
1993	132.8
1994	132.5
1995	132.2
1996	132
1997	131.8
1998	131.7
1999	131.6
2000	131.6
2001	131.7
2002	131.8
2003	131.9
2004	132.1
2005	132.3
2006	132.4
2007	132.6
2008	132.8