Year	mm Hg
1980	136.2
1981	136.1
1982	135.9
1983	135.8
1984	135.6
1985	135.4
1986	135.2
1987	135.1
1988	134.9
1989	134.8
1990	134.6
1991	134.4
1992	134
1993	133.6
1994	133.4
1995	133.2
1996	133.1
1997	132.9
1998	132.8
1999	132.7
2000	132.6
2001	132.6
2002	132.6
2003	132.6
2004	132.6
2005	132.7
2006	132.8
2007	132.8
2008	132.8