Year	mm Hg
1980	130.9
1981	131.2
1982	131.6
1983	131.8
1984	132.1
1985	132.3
1986	132.5
1987	132.7
1988	132.8
1989	132.9
1990	133
1991	133.1
1992	133.2
1993	133.3
1994	133.4
1995	133.5
1996	133.5
1997	133.6
1998	133.7
1999	133.8
2000	133.9
2001	134
2002	134.1
2003	134.2
2004	134.3
2005	134.3
2006	134.3
2007	134.2
2008	134.2