Year	mm Hg
1980	138.3
1981	137.7
1982	137.1
1983	136.5
1984	135.9
1985	135.4
1986	135
1987	134.7
1988	134.4
1989	134.1
1990	133.9
1991	133.6
1992	133.3
1993	133
1994	132.7
1995	132.4
1996	132.1
1997	131.8
1998	131.6
1999	131.3
2000	131.1
2001	131
2002	130.9
2003	130.8
2004	130.7
2005	130.7
2006	130.6
2007	130.6
2008	130.6