Year	mm Hg
1980	136.6
1981	136.5
1982	136.3
1983	136.1
1984	135.9
1985	135.7
1986	135.5
1987	135.3
1988	135.1
1989	134.9
1990	134.7
1991	134.4
1992	134
1993	133.6
1994	133.2
1995	132.8
1996	132.4
1997	132.2
1998	131.9
1999	131.6
2000	131.3
2001	131.1
2002	130.9
2003	130.9
2004	130.8
2005	130.7
2006	130.6
2007	130.5
2008	130.4