Year	mm Hg
1980	139.6
1981	139
1982	138.4
1983	137.8
1984	137.3
1985	136.8
1986	136.4
1987	136.2
1988	136
1989	135.8
1990	135.7
1991	135.6
1992	135.4
1993	135.1
1994	134.9
1995	134.6
1996	134.2
1997	133.9
1998	133.6
1999	133.3
2000	133
2001	132.7
2002	132.4
2003	132.1
2004	131.9
2005	131.6
2006	131.4
2007	131.2
2008	130.9