Year	mm Hg
1980	136.2
1981	136.3
1982	136.3
1983	136.4
1984	136.3
1985	136.3
1986	136.2
1987	136.1
1988	136
1989	135.8
1990	135.5
1991	135.2
1992	134.9
1993	134.5
1994	134.2
1995	134
1996	133.8
1997	133.5
1998	133.3
1999	133.3
2000	133.2
2001	133.2
2002	133.3
2003	133.4
2004	133.5
2005	133.6
2006	133.8
2007	133.9
2008	134