Year	mm Hg
1980	136.6
1981	136.3
1982	136.1
1983	135.8
1984	135.6
1985	135.4
1986	135.2
1987	135.2
1988	135.2
1989	135.2
1990	135.1
1991	134.9
1992	134.8
1993	134.5
1994	134.3
1995	134
1996	133.7
1997	133.3
1998	133
1999	132.6
2000	132.3
2001	132.1
2002	131.8
2003	131.6
2004	131.4
2005	131.3
2006	131.1
2007	131
2008	130.9