Year	mm Hg
1980	120.4
1981	120
1982	119.8
1983	119.6
1984	119.4
1985	119.2
1986	119.1
1987	119.1
1988	119.1
1989	119.1
1990	119.2
1991	119.3
1992	119.4
1993	119.5
1994	119.7
1995	119.8
1996	120
1997	120.2
1998	120.4
1999	120.6
2000	120.8
2001	121
2002	121.1
2003	121.3
2004	121.4
2005	121.6
2006	121.7
2007	121.8
2008	122