Year	mm Hg
1980	134.6
1981	134.7
1982	134.8
1983	134.8
1984	134.8
1985	134.7
1986	134.6
1987	134.4
1988	134.2
1989	134
1990	133.7
1991	133.4
1992	133
1993	132.6
1994	132.3
1995	131.9
1996	131.6
1997	131.3
1998	131.1
1999	131
2000	131
2001	131
2002	131.1
2003	131.2
2004	131.4
2005	131.6
2006	131.9
2007	132.1
2008	132.3