Year	mm Hg
1980	136.8
1981	136.8
1982	136.9
1983	136.9
1984	136.8
1985	136.7
1986	136.6
1987	136.5
1988	136.3
1989	136.1
1990	135.9
1991	135.5
1992	135.2
1993	134.8
1994	134.4
1995	134.1
1996	133.9
1997	133.7
1998	133.6
1999	133.6
2000	133.7
2001	133.8
2002	133.9
2003	134.1
2004	134.2
2005	134.4
2006	134.6
2007	134.8
2008	135