Year	mm Hg
1980	131.7
1981	131.5
1982	131.4
1983	131.3
1984	131.2
1985	131.2
1986	131.1
1987	130.9
1988	130.8
1989	130.7
1990	130.5
1991	130.4
1992	130.2
1993	130
1994	129.9
1995	129.7
1996	129.6
1997	129.5
1998	129.4
1999	129.4
2000	129.4
2001	129.4
2002	129.4
2003	129.4
2004	129.5
2005	129.5
2006	129.5
2007	129.6
2008	129.6