Year	% of total
1971	15.834196369121011
1972	21.26080568426573
1973	20.106941022899818
1974	20.9261042279001
1975	17.826263785169992
1976	16.822244714250566
1977	14.22482628079002
1978	20.38402900819976
1979	19.955656627143643
1980	19.963064235226515
1981	19.15939481407926
1982	16.61654958456971
1983	17.623405477071643
1984	17.065248811841624
1985	20.307574107072
1986	19.891288821989157
1987	20.384236020584254
1988	22.017964903357925
1989	22.103251062121277
1990	25.480388417373263
1991	25.48286108942486
1992	24.09807593163865
1993	24.964661821441624
1994	24.43968301591525
1995	22.780196328283093
1996	23.49809695198801
1997	23.87447372214146
1998	22.124865438963834
1999	24.714412920566193
2000	25.220051917635516
2001	26.679299976953647
2002	28.14780415428756
2003	31.721424119365594
2004	31.561637186568586
2005	27.083771467797536
2006	31.67467435514374
2007	34.742475817209275
2008	37.96075957289015
2009	41.799331243804275
2010	42.9925150346511
2011	43.84978389955335
2012	48.01005976908591
2013	46.50855391849568
2014	48.305593009732874