Year	mm Hg
1980	121.8
1981	121.8
1982	121.7
1983	121.6
1984	121.4
1985	121.2
1986	121
1987	120.9
1988	120.8
1989	120.8
1990	120.9
1991	120.9
1992	120.9
1993	121
1994	120.9
1995	120.9
1996	120.8
1997	120.7
1998	120.6
1999	120.5
2000	120.5
2001	120.5
2002	120.5
2003	120.6
2004	120.7
2005	120.7
2006	120.8
2007	120.9
2008	120.9