Year	mm Hg
1980	134.8
1981	134.6
1982	134.3
1983	134
1984	133.6
1985	133.2
1986	132.9
1987	132.7
1988	132.5
1989	132.3
1990	132.1
1991	131.9
1992	131.8
1993	131.6
1994	131.6
1995	131.5
1996	131.4
1997	131.4
1998	131.5
1999	131.5
2000	131.6
2001	131.6
2002	131.6
2003	131.6
2004	131.7
2005	131.9
2006	132
2007	132.1
2008	132.3