Year	mm Hg
1980	135.8
1981	135.7
1982	135.5
1983	135.4
1984	135.2
1985	135
1986	134.8
1987	134.5
1988	134.3
1989	134
1990	133.8
1991	133.4
1992	133
1993	132.6
1994	132.2
1995	131.9
1996	131.7
1997	131.4
1998	131.2
1999	131
2000	130.8
2001	130.6
2002	130.4
2003	130.3
2004	130.1
2005	130
2006	129.8
2007	129.7
2008	129.5