Year	% of total
1970	1.769832601066646
1971	2.1616017909668526
1972	2.12700226480479
1973	2.0947886813798253
1974	2.1641803807853854
1975	2.0972826501833706
1976	2.2049677293101793
1977	2.095903651560572
1978	2.0547207236288605
1979	1.991329266473823
1980	2.539189724327647
1981	3.1243812711786347
1982	3.5236382629759366
1983	4.031883318736326
1984	4.774719565699746
1985	5.296676091300275
1986	5.806794283936226
1987	6.009770690817275
1988	6.96838233940399
1989	7.233487652976418
1990	6.83411214953271
1991	7.297139521307646
1992	7.7011494252873565
1993	7.995495495495495
1994	8.633504859919954
1995	8.956916099773244
1996	9.219457013574662
1997	9.491525423728813
1998	9.466152999449642
1999	9.816971713810316
2000	10.207515423443635
2001	11.274221961244862
2002	12.523248605083696
2003	12.325581395348838
2004	13.269575612671847
2005	12.346993081426291
2006	12.191103789126853
2007	11.205523101433883
2008	10.995052226498075