Year	mm Hg
1980	135.4
1981	135.3
1982	135.1
1983	134.9
1984	134.8
1985	134.5
1986	134.3
1987	134.1
1988	133.9
1989	133.8
1990	133.6
1991	133.3
1992	133.1
1993	132.7
1994	132.4
1995	132.1
1996	131.8
1997	131.6
1998	131.4
1999	131.3
2000	131.3
2001	131.4
2002	131.6
2003	131.9
2004	132.2
2005	132.5
2006	132.9
2007	133.4
2008	133.8