Year	% of total
1970	3.113555309226497
1971	2.615935288817211
1972	2.596395411709298
1973	2.5604513058362066
1974	2.386328002218581
1975	2.177624183423
1976	2.2357437141737098
1977	2.269942672973352
1978	2.277548498330177
1979	2.6201059472914294
1980	3.1181802081078516
1981	3.6699005083502345
1982	3.940648966042806
1983	3.9162919974804886
1984	4.714084350423654
1985	5.634432386270728
1986	6.424778330860052
1987	7.194550188802924
1988	7.290464181479847
1989	7.546934620831614
1990	4.17607223476298
1991	4.8997772828507795
1992	5.128205128205128
1993	5.598243688254665
1994	6.584821428571429
1995	8.194905869324474
1996	9.371554575523705
1997	9.821428571428571
1998	10.05586592178771
1999	10.983981693363845
2000	10.520231213872833
2001	10.573678290213723
2002	10.532407407407407
2003	10.409356725146198
2004	10.9375
2005	10.442260442260443
2006	9.975062344139651
2007	9.339975093399751
2008	9.230769230769232