Year	mm Hg
1980	139.9
1981	139.4
1982	138.9
1983	138.4
1984	137.9
1985	137.4
1986	136.9
1987	136.5
1988	136.1
1989	135.7
1990	135.3
1991	134.9
1992	134.5
1993	134.1
1994	133.8
1995	133.4
1996	133.2
1997	133
1998	132.8
1999	132.7
2000	132.7
2001	132.7
2002	132.7
2003	132.7
2004	132.8
2005	132.9
2006	133.1
2007	133.3
2008	133.5