Year	mm Hg
1980	138.8
1981	138.3
1982	137.7
1983	137.2
1984	136.7
1985	136.2
1986	135.8
1987	135.5
1988	135.2
1989	135
1990	134.8
1991	134.6
1992	134.4
1993	134.2
1994	134
1995	133.8
1996	133.6
1997	133.4
1998	133.2
1999	133.1
2000	132.9
2001	132.7
2002	132.4
2003	132.2
2004	132
2005	131.7
2006	131.5
2007	131.3
2008	131