Year	mm Hg
1980	134.3
1981	134
1982	133.7
1983	133.4
1984	133.2
1985	133
1986	132.8
1987	132.8
1988	132.8
1989	132.8
1990	132.9
1991	132.8
1992	132.8
1993	132.7
1994	132.6
1995	132.4
1996	132.3
1997	132.2
1998	132.1
1999	132
2000	131.9
2001	131.8
2002	131.7
2003	131.6
2004	131.6
2005	131.5
2006	131.4
2007	131.3
2008	131.2