Year	mm Hg
1980	122.9
1981	122.7
1982	122.5
1983	122.2
1984	122
1985	121.8
1986	121.6
1987	121.4
1988	121.2
1989	121.1
1990	121
1991	120.9
1992	120.8
1993	120.7
1994	120.6
1995	120.5
1996	120.3
1997	120.2
1998	120.1
1999	120
2000	119.9
2001	119.9
2002	119.8
2003	119.8
2004	119.8
2005	119.8
2006	119.8
2007	119.9
2008	119.9