Year	per person
1800	1.988
1820	2.03
1913	4.524
1950	8.865
1973	18.23
1990	22.78
1991	20.63
1992	18.08
1993	16.96
1994	16.96
1995	17.98
1996	19.04
1997	21.25
1998	22.55
1999	22.71
2000	24.66
2001	26.43
2002	28.53
2003	30.2
2004	32.93
2005	36.52
2006	40.24
2007	43.21
2008	41.65
2009	35.85