Year	mm Hg
1980	136.6
1981	136.4
1982	136.1
1983	135.8
1984	135.5
1985	135.2
1986	134.9
1987	134.7
1988	134.3
1989	134
1990	133.6
1991	133.2
1992	132.8
1993	132.4
1994	131.9
1995	131.6
1996	131.2
1997	131
1998	130.8
1999	130.7
2000	130.7
2001	130.8
2002	131
2003	131.2
2004	131.5
2005	131.9
2006	132.3
2007	132.9
2008	133.4