Year	mm Hg
1980	140.1
1981	140
1982	139.9
1983	139.8
1984	139.7
1985	139.5
1986	139.3
1987	139.1
1988	139
1989	138.8
1990	138.5
1991	138.3
1992	138
1993	137.6
1994	137.2
1995	136.9
1996	136.6
1997	136.3
1998	136
1999	135.9
2000	135.9
2001	135.9
2002	136
2003	136.1
2004	136.3
2005	136.6
2006	136.8
2007	137.1
2008	137.3