Year	mm Hg
1980	135.1
1981	135.1
1982	135.1
1983	135.1
1984	135.1
1985	135.1
1986	135.1
1987	135.1
1988	135
1989	135
1990	135
1991	134.9
1992	134.8
1993	134.7
1994	134.7
1995	134.6
1996	134.5
1997	134.4
1998	134.5
1999	134.6
2000	134.7
2001	134.8
2002	134.9
2003	135.1
2004	135.3
2005	135.6
2006	135.9
2007	136.2
2008	136.6