Year	mm Hg
1980	133.7
1981	133.7
1982	133.7
1983	133.7
1984	133.7
1985	133.6
1986	133.4
1987	133.3
1988	133.1
1989	132.8
1990	132.5
1991	132.1
1992	131.7
1993	131.3
1994	131
1995	130.7
1996	130.5
1997	130.2
1998	130
1999	129.8
2000	129.6
2001	129.5
2002	129.3
2003	129.3
2004	129.2
2005	129.1
2006	129
2007	128.9
2008	128.8