Year	mm Hg
1980	138.7
1981	138.1
1982	137.5
1983	136.9
1984	136.3
1985	135.8
1986	135.3
1987	135
1988	134.7
1989	134.4
1990	134.1
1991	133.9
1992	133.7
1993	133.4
1994	133.2
1995	133
1996	132.8
1997	132.6
1998	132.4
1999	132.3
2000	132.1
2001	132
2002	131.9
2003	131.8
2004	131.6
2005	131.5
2006	131.4
2007	131.3
2008	131.2