Year	per person
1800	1.531
1820	1.531
1913	2.825
1970	22.19
1971	23.35
1972	24.22
1973	25.01
1974	26.18
1975	26.66
1976	28.1
1977	38.02
1978	40.21
1979	41.77
1980	44.97
1981	45.1
1982	43.88
1983	43.25
1984	42.06
1985	40.77
1986	38.13
1987	38.17
1988	38.35
1989	40.97
1990	41.3
1991	41.85
1992	43.05
1993	45
1994	47.57
1995	48.6
1996	49.74
1997	51.03
1998	50.22
1999	49.88
2000	48.87
2001	49.57
2002	49.55
2003	49.87
2004	49.92
2005	49.78
2006	49.99
2007	50.53
2008	50.83