Year	mm Hg
1980	137.8
1981	137.6
1982	137.4
1983	137.2
1984	137
1985	136.8
1986	136.5
1987	136.2
1988	135.9
1989	135.5
1990	135.1
1991	134.6
1992	134
1993	133.5
1994	133
1995	132.6
1996	132.3
1997	132.1
1998	132
1999	131.8
2000	131.7
2001	131.7
2002	131.6
2003	131.5
2004	131.3
2005	131.2
2006	131.1
2007	130.9
2008	130.8