Year	% of total
1970	12.464606499817709
1971	12.752957733830254
1972	12.98211210752474
1973	11.937262088724465
1974	14.136453655199222
1975	13.34725759055742
1976	12.84470563879602
1977	11.611780124060507
1978	13.648377330803296
1979	13.099129823626013
1980	10.434564745381254
1981	12.278305955991343
1982	11.167115256977768
1983	12.209800331250435
1984	12.604864342661415
1985	14.803089435697236
1986	15.918757083538718
1987	15.553079007208403
1988	16.91875534348807
1989	15.619976995663375
1990	22.491909385113267
1991	21.875
1992	21.148036253776432
1993	20.55393586005831
1994	19.91584852734923
1995	19.18918918918919
1996	19.91643454038997
1997	19.51219512195122
1998	18.377693282636248
1999	18.64623243933589
2000	17.90499390986602
2001	17.229336437718278
2002	16.195652173913043
2003	16.077170418006432
2004	16.046758767268862
2005	14.931237721021612
2006	14.725697786333011
2007	14.473684210526317
2008	14.129443938012761