Year	mm Hg
1980	135.3
1981	135
1982	134.7
1983	134.4
1984	134
1985	133.7
1986	133.3
1987	133
1988	132.7
1989	132.5
1990	132.2
1991	132
1992	131.8
1993	131.6
1994	131.4
1995	131.2
1996	131.1
1997	130.9
1998	130.8
1999	130.7
2000	130.7
2001	130.6
2002	130.6
2003	130.6
2004	130.6
2005	130.6
2006	130.6
2007	130.5
2008	130.5