Year	mm Hg
1980	131.1
1981	131
1982	130.8
1983	130.6
1984	130.4
1985	130.2
1986	130
1987	129.7
1988	129.5
1989	129.3
1990	129.1
1991	128.9
1992	128.7
1993	128.5
1994	128.4
1995	128.4
1996	128.4
1997	128.4
1998	128.6
1999	128.8
2000	129
2001	129.3
2002	129.6
2003	130
2004	130.3
2005	130.6
2006	131
2007	131.3
2008	131.6