Year	mm Hg
1980	138.8
1981	138.1
1982	137.4
1983	136.8
1984	136.1
1985	135.5
1986	135.1
1987	134.8
1988	134.6
1989	134.4
1990	134.2
1991	134
1992	133.8
1993	133.6
1994	133.5
1995	133.3
1996	133.2
1997	133.1
1998	133.1
1999	133
2000	132.9
2001	132.8
2002	132.7
2003	132.6
2004	132.4
2005	132.3
2006	132.1
2007	131.9
2008	131.7