Year	mm Hg
1980	134.8
1981	134.8
1982	134.8
1983	134.7
1984	134.7
1985	134.6
1986	134.6
1987	134.5
1988	134.4
1989	134.3
1990	134.1
1991	133.9
1992	133.6
1993	133.1
1994	132.7
1995	132.2
1996	131.8
1997	131.6
1998	131.4
1999	131.3
2000	131.2
2001	131.2
2002	131.3
2003	131.3
2004	131.4
2005	131.5
2006	131.7
2007	131.9
2008	132.1