Year	mm Hg
1980	135.2
1981	134.8
1982	134.6
1983	134.3
1984	134.1
1985	133.9
1986	133.8
1987	133.7
1988	133.7
1989	133.6
1990	133.6
1991	133.5
1992	133.3
1993	133.1
1994	132.9
1995	132.7
1996	132.6
1997	132.5
1998	132.4
1999	132.4
2000	132.4
2001	132.5
2002	132.6
2003	132.7
2004	132.8
2005	133
2006	133.2
2007	133.4
2008	133.6