Year	mm Hg
1980	135.9
1981	135.9
1982	135.8
1983	135.8
1984	135.7
1985	135.7
1986	135.6
1987	135.6
1988	135.6
1989	135.7
1990	135.8
1991	135.8
1992	135.9
1993	135.9
1994	136
1995	135.9
1996	135.9
1997	135.8
1998	135.8
1999	135.7
2000	135.6
2001	135.6
2002	135.6
2003	135.6
2004	135.6
2005	135.6
2006	135.6
2007	135.8
2008	135.9