Year	mm Hg
1980	131.5
1981	131.6
1982	131.7
1983	131.7
1984	131.7
1985	131.8
1986	131.8
1987	131.9
1988	131.9
1989	132
1990	132
1991	132.1
1992	132.3
1993	132.4
1994	132.5
1995	132.6
1996	132.7
1997	133
1998	133.2
1999	133.5
2000	133.7
2001	134
2002	134.3
2003	134.7
2004	135
2005	135.3
2006	135.6
2007	136
2008	136.3