Year	mm Hg
1980	134.4
1981	134.3
1982	134.3
1983	134.2
1984	134.1
1985	134
1986	133.8
1987	133.6
1988	133.4
1989	133.2
1990	132.9
1991	132.6
1992	132.2
1993	131.8
1994	131.4
1995	131
1996	130.7
1997	130.4
1998	130.1
1999	130
2000	129.9
2001	129.8
2002	129.8
2003	129.8
2004	129.8
2005	129.8
2006	129.8
2007	129.8
2008	129.8