Year	% of total
1960	0.242338961851157
1961	0.23103294082575648
1962	0.2048760499897562
1963	0.29669677589503524
1964	0.28438469493278185
1965	0.34460338101430427
1966	0.38207116788321166
1967	0.38779015013018664
1968	0.298394354189362
1969	0.27834558343843774
1970	0.16426141030153701
1971	0.24295258851691737
1972	0.24048481739186198
1973	0.2851368933920217
1974	0.48311648475243474
1975	0.5167018412051525
1976	0.5908628961735719
1977	0.6953195319531954
1978	0.8394130326645663
1979	0.8665005062699589
1980	1.0074480595844766
1981	0.9818150772645776
1982	1.3843630864907461
1983	2.0290046433837285
1984	2.472085849589434
1985	2.757602120298622
1986	3.012759053027509
1987	3.201752835989681
1988	3.2700458892352957
1989	3.4164310802707107
1990	3.745422677292445
1991	3.540465444975144
1992	3.7397565417425476
1993	3.960455432661028
1994	3.9696197018678165
1995	3.928169358178054
1996	4.043603271205782
1997	4.191824801960855
1998	4.2589967670931355
1999	4.631627636218482
2000	5.764321808935939
2001	7.166233258230066
2002	8.935191944024206
2003	9.44280652982059
2004	11.04723589178602
2005	11.582043811079847
2006	11.998615485957243
2007	11.543872894856621
2008	13.050681158641444
2009	11.16102556793889
2010	13.250728886430494
2011	12.112563770617568
2012	13.253669204887549
2013	14.732248063620926
2014	15.410256718891826
2015	16.09302414734254
2016	14.961419746102148