Year	Percent
1972	13.68095
1973	10.44732
1974	12.71036
1975	12.23613
1976	15.52333
1977	15.84769
1978	16.02307
1979	14.447
1980	15.82578
1981	16.73906
1982	14.00555
1983	15.1213
1984	13.86926
1985	15.94975
1986	16.76323
1987	15.96545
1988	15.1891
1989	14.53218
1990	16.20259
1991	16.79324
1992	17.24086
1993	19.38949
1994	19.03441
1995	16.87876
1996	17.3511
1997	16.78079
1998	16.98284
1999	15.27829
2000	14.69914
2001	15.30598
2002	15.77768
2003	17.20601
2004	17.8462
2005	17.89692
2006	18.98806
2007	18.41051
2008	18.24184
2009	18.72222
2010	18.88639
2011	19.10183
2012	18.82189
2013	19.04141
2014	18.56672
2015	18.50948
2016	23.7093