Year	mm Hg
1980	123
1981	122.9
1982	122.8
1983	122.6
1984	122.4
1985	122.2
1986	122
1987	121.8
1988	121.7
1989	121.5
1990	121.4
1991	121.3
1992	121.1
1993	121
1994	120.9
1995	120.8
1996	120.6
1997	120.5
1998	120.4
1999	120.4
2000	120.4
2001	120.4
2002	120.4
2003	120.4
2004	120.5
2005	120.6
2006	120.7
2007	120.8
2008	121