Year	mm Hg
1980	134.3
1981	133.9
1982	133.4
1983	133
1984	132.5
1985	132
1986	131.5
1987	131.1
1988	130.8
1989	130.5
1990	130.2
1991	129.9
1992	129.6
1993	129.3
1994	129.1
1995	128.8
1996	128.6
1997	128.3
1998	128.1
1999	127.9
2000	127.8
2001	127.7
2002	127.6
2003	127.6
2004	127.7
2005	127.7
2006	127.8
2007	127.8
2008	127.8