Year	mm Hg
1980	122.4
1981	122.3
1982	122.1
1983	122
1984	121.9
1985	121.8
1986	121.8
1987	121.8
1988	121.8
1989	121.8
1990	121.9
1991	121.9
1992	121.9
1993	121.8
1994	121.8
1995	121.8
1996	121.7
1997	121.6
1998	121.5
1999	121.5
2000	121.4
2001	121.4
2002	121.4
2003	121.4
2004	121.5
2005	121.5
2006	121.5
2007	121.5
2008	121.5