Year	mm Hg
1980	131.8
1981	131.6
1982	131.4
1983	131.3
1984	131.2
1985	131.3
1986	131.3
1987	131.3
1988	131.2
1989	130.9
1990	130.8
1991	130.8
1992	130.7
1993	130.6
1994	130.5
1995	130.4
1996	130.3
1997	130.2
1998	130.1
1999	129.9
2000	129.6
2001	129.4
2002	129.1
2003	128.9
2004	128.6
2005	128.3
2006	128
2007	127.8
2008	127.5