Year	mm Hg
1980	138.6
1981	138.4
1982	138.2
1983	137.9
1984	137.7
1985	137.4
1986	137.1
1987	136.9
1988	136.6
1989	136.4
1990	136.2
1991	136
1992	135.8
1993	135.6
1994	135.3
1995	135
1996	134.7
1997	134.3
1998	133.9
1999	133.6
2000	133.2
2001	132.8
2002	132.4
2003	132.1
2004	131.7
2005	131.2
2006	130.8
2007	130.4
2008	129.9