Year	mm Hg
1980	135.5
1981	135.3
1982	135.1
1983	134.9
1984	134.7
1985	134.4
1986	134.3
1987	134.2
1988	134
1989	133.9
1990	133.8
1991	133.7
1992	133.6
1993	133.4
1994	133.3
1995	133.1
1996	133
1997	133
1998	132.9
1999	133
2000	133
2001	133.1
2002	133.2
2003	133.4
2004	133.5
2005	133.6
2006	133.7
2007	133.8
2008	133.9