Year	mm Hg
1980	139.3
1981	138.6
1982	138
1983	137.3
1984	136.6
1985	135.9
1986	135.2
1987	134.5
1988	134
1989	133.5
1990	133
1991	132.6
1992	132.2
1993	131.8
1994	131.5
1995	131.2
1996	131
1997	130.8
1998	130.8
1999	130.7
2000	130.7
2001	130.7
2002	130.7
2003	130.7
2004	130.7
2005	130.7
2006	130.7
2007	130.7
2008	130.6