Year	mm Hg
1980	136.5
1981	136.3
1982	136.2
1983	136
1984	135.9
1985	135.8
1986	135.8
1987	135.9
1988	136.1
1989	136.4
1990	136.5
1991	136.7
1992	136.7
1993	136.7
1994	136.6
1995	136.4
1996	136.2
1997	135.9
1998	135.5
1999	135.2
2000	134.8
2001	134.4
2002	133.9
2003	133.5
2004	133
2005	132.6
2006	132.1
2007	131.7
2008	131.2