Year	mm Hg
1980	137.7
1981	137.4
1982	136.9
1983	136.2
1984	135.7
1985	135
1986	134.2
1987	133.5
1988	132.8
1989	132.1
1990	131.5
1991	131
1992	130.5
1993	130.1
1994	129.7
1995	129.3
1996	129.1
1997	128.9
1998	128.6
1999	128.4
2000	128.2
2001	128.1
2002	128
2003	128.1
2004	128.1
2005	128.1
2006	128.1
2007	128.1
2008	128.1