Year	mm Hg
1980	135.3
1981	134.9
1982	134.6
1983	134.2
1984	133.8
1985	133.5
1986	133.2
1987	133
1988	132.9
1989	132.7
1990	132.6
1991	132.5
1992	132.3
1993	132.1
1994	131.8
1995	131.6
1996	131.3
1997	130.9
1998	130.6
1999	130.2
2000	129.9
2001	129.5
2002	129.2
2003	128.8
2004	128.5
2005	128.2
2006	127.9
2007	127.6
2008	127.3