Year	per person
1800	1.283
1820	1.31
1913	2.92
1950	5.722
1973	15.89
1990	15.54
1991	13.74
1992	12.98
1993	11.85
1994	10.53
1995	9.853
1996	10.02
1997	10.33
1998	10.29
1999	10.68
2000	11.77
2001	13.34
2002	14.62
2003	15.95
2004	17.39
2005	19.08
2006	20.7
2007	22.34
2008	23.03
2009	23.27