Year	mm Hg
1980	137.5
1981	137.1
1982	136.6
1983	136.2
1984	135.8
1985	135.3
1986	134.8
1987	134.3
1988	133.9
1989	133.5
1990	133
1991	132.6
1992	132.2
1993	131.8
1994	131.5
1995	131.2
1996	130.9
1997	130.7
1998	130.6
1999	130.4
2000	130.3
2001	130.2
2002	130.1
2003	130
2004	129.9
2005	129.8
2006	129.8
2007	129.7
2008	129.7