Year	mm Hg
1980	138.4
1981	138
1982	137.6
1983	137.2
1984	136.8
1985	136.3
1986	135.9
1987	135.5
1988	135.1
1989	134.8
1990	134.4
1991	134.1
1992	133.8
1993	133.6
1994	133.3
1995	133.1
1996	132.9
1997	132.8
1998	132.6
1999	132.5
2000	132.5
2001	132.5
2002	132.6
2003	132.7
2004	132.9
2005	133
2006	133.2
2007	133.4
2008	133.6