Year	per person
1800	1.257
1820	1.257
1913	1.7
1950	2.126
1960	2.456
1961	2.562
1962	2.675
1963	2.732
1964	2.908
1965	3.141
1966	3.255
1967	3.316
1968	3.385
1969	3.584
1970	3.884
1971	4.034
1972	4.163
1973	4.333
1974	4.345
1975	4.211
1976	3.98
1977	3.929
1978	4.174
1979	4.158
1980	3.969
1981	3.862
1982	3.778
1983	3.799
1984	3.688
1985	3.737
1986	3.814
1987	3.821
1988	3.834
1989	3.685
1990	3.483
1991	3.718
1992	4.125
1993	4.75
1994	4.901
1995	4.614
1996	4.839
1997	4.526
1998	4.24
1999	4.205
2000	3.995
2001	3.89
2002	3.788
2003	3.777
2004	3.791
2005	3.831
2006	3.829
2007	4.009
2008	4.179
2009	4.27