Year	mm Hg
1980	134.4
1981	133.7
1982	133.1
1983	132.5
1984	132
1985	131.5
1986	131.1
1987	130.8
1988	130.7
1989	130.6
1990	130.6
1991	130.6
1992	130.6
1993	130.5
1994	130.5
1995	130.6
1996	130.6
1997	130.7
1998	130.7
1999	130.7
2000	130.8
2001	130.8
2002	130.8
2003	130.8
2004	130.8
2005	130.8
2006	130.8
2007	130.8
2008	130.8