Year	mm Hg
1980	136.6
1981	136.2
1982	135.8
1983	135.3
1984	134.8
1985	134.4
1986	134.1
1987	133.9
1988	133.7
1989	133.5
1990	133.4
1991	133.3
1992	133.3
1993	133.2
1994	133.1
1995	133
1996	132.9
1997	132.8
1998	132.7
1999	132.6
2000	132.5
2001	132.5
2002	132.4
2003	132.3
2004	132.2
2005	132.1
2006	132
2007	131.9
2008	131.8