Year	mm Hg
1980	135.1
1981	135.1
1982	135
1983	134.9
1984	134.7
1985	134.6
1986	134.5
1987	134.4
1988	134.3
1989	134.1
1990	134
1991	133.8
1992	133.4
1993	132.9
1994	132.5
1995	132.1
1996	131.8
1997	131.6
1998	131.4
1999	131.3
2000	131.2
2001	131.1
2002	131
2003	130.9
2004	130.8
2005	130.8
2006	130.7
2007	130.6
2008	130.6