Year	mm Hg
1980	140.9
1981	140.5
1982	140
1983	139.4
1984	138.8
1985	138.2
1986	137.6
1987	137.1
1988	136.5
1989	136.1
1990	135.7
1991	135.4
1992	135.1
1993	134.9
1994	134.8
1995	134.7
1996	134.7
1997	134.7
1998	134.9
1999	135.1
2000	135.4
2001	135.8
2002	136.2
2003	136.7
2004	137.2
2005	137.7
2006	138.3
2007	138.9
2008	139.4