Year	% of total
1970	52.77482837216614
1971	52.19574428020333
1972	52.31768738613689
1973	51.87704909067329
1974	49.526220505820724
1975	48.82231579459381
1976	47.31506148161828
1977	49.169918896349145
1978	50.97123942296792
1979	51.03396473979739
1980	52.35416680577622
1981	51.61999932353187
1982	51.63691396322662
1983	49.56043197167745
1984	47.998334452520204
1985	47.59672239869784
1986	47.06063845960727
1987	46.144057466989366
1988	45.99903785666415
1989	43.871206143715085
1990	47.217235188509875
1991	46.215494211932324
1992	44.69964664310954
1993	42.95837023914969
1994	42.94268605645851
1995	41.84873949579832
1996	42.19269102990033
1997	41.48936170212766
1998	40.44943820224719
1999	40.271132376395535
2000	39.71291866028708
2001	37.71289537712895
2002	36.624203821656046
2003	35.797665369649806
2004	35.43913713405239
2005	37.0429252782194
2006	36.90572119258662
2007	37.40831295843521
2008	38.917089678511