Year	mm Hg
1980	131.9
1981	132.1
1982	132.3
1983	132.4
1984	132.5
1985	132.6
1986	132.7
1987	132.8
1988	132.9
1989	133
1990	133
1991	133.1
1992	133
1993	132.8
1994	132.7
1995	132.7
1996	132.7
1997	132.9
1998	133
1999	133
2000	133.1
2001	133.1
2002	133.1
2003	133.2
2004	133.3
2005	133.3
2006	133.3
2007	133.2
2008	133.2