Year	mm Hg
1980	136.5
1981	136.1
1982	135.8
1983	135.4
1984	135
1985	134.6
1986	134.3
1987	134.1
1988	133.8
1989	133.6
1990	133.4
1991	133.2
1992	133
1993	132.9
1994	132.7
1995	132.5
1996	132.3
1997	132.2
1998	132.1
1999	132
2000	131.9
2001	131.8
2002	131.8
2003	131.7
2004	131.7
2005	131.7
2006	131.9
2007	132
2008	132.1