Year	mm Hg
1980	141.3
1981	140.6
1982	139.9
1983	139.1
1984	138.4
1985	137.7
1986	137.1
1987	136.6
1988	136.2
1989	135.9
1990	135.5
1991	135.1
1992	134.7
1993	134.3
1994	133.9
1995	133.6
1996	133.3
1997	133.1
1998	132.9
1999	132.8
2000	132.7
2001	132.7
2002	132.7
2003	132.7
2004	132.7
2005	132.8
2006	132.9
2007	133
2008	133.1