Year	mm Hg
1980	136.6
1981	135.9
1982	135.2
1983	134.6
1984	133.9
1985	133.3
1986	132.8
1987	132.4
1988	132.1
1989	131.9
1990	131.6
1991	131.4
1992	131.2
1993	131
1994	130.8
1995	130.7
1996	130.6
1997	130.5
1998	130.4
1999	130.4
2000	130.3
2001	130.3
2002	130.3
2003	130.3
2004	130.2
2005	130.3
2006	130.3
2007	130.4
2008	130.4