Year	Years
1800	381.4
1900	379.3
1931	289
1979	127.2
1980	118.7
1981	110.4
1982	103
1983	96.4
1984	90.4
1985	85.2
1986	80.8
1987	77.1
1988	74.2
1989	72.3
1990	71.4
1991	71.1
1992	71
1993	70.7
1994	70.3
1995	69.7
1996	69.1
1997	68.2
1998	67.1
1999	65.7
2000	63.9
2001	62
2002	60.2
2003	58.4
2004	56.7
2005	54.9
2006	53.2
2007	51.5
2008	49.9
2009	48.3
2010	46.8
2011	45.4
2012	43.9
2013	42.5