Year	mm Hg
1980	135
1981	135.2
1982	135.3
1983	135.5
1984	135.7
1985	135.7
1986	135.8
1987	135.8
1988	135.8
1989	135.8
1990	135.7
1991	135.5
1992	135.3
1993	135.1
1994	134.9
1995	134.7
1996	134.5
1997	134.3
1998	134.1
1999	133.9
2000	133.9
2001	133.8
2002	133.8
2003	133.8
2004	133.9
2005	133.9
2006	134
2007	134.1
2008	134.2