Year	mm Hg
1980	142.1
1981	141.5
1982	140.8
1983	140.2
1984	139.6
1985	139.1
1986	138.6
1987	138.2
1988	137.9
1989	137.7
1990	137.4
1991	137.1
1992	136.9
1993	136.6
1994	136.4
1995	136.2
1996	136
1997	135.9
1998	135.7
1999	135.5
2000	135.4
2001	135.3
2002	135.1
2003	135
2004	134.9
2005	134.8
2006	134.7
2007	134.6
2008	134.5