Year	mm Hg
1980	137.7
1981	137.4
1982	137.1
1983	136.8
1984	136.5
1985	136.1
1986	135.8
1987	135.4
1988	134.9
1989	134.4
1990	133.9
1991	133.3
1992	132.6
1993	132.1
1994	131.5
1995	131.2
1996	130.9
1997	130.7
1998	130.5
1999	130.3
2000	130.2
2001	130.1
2002	130
2003	129.9
2004	129.8
2005	129.7
2006	129.6
2007	129.6
2008	129.5