Year	Percent
1971	13.35465
1972	13.63609
1973	14.85808
1974	18.30874
1975	14.88884
1976	25.56322
1977	39.47828
1978	50.33893
1979	64.95421
1980	57.95294
1981	36.07125
1982	30.58904
1983	26.80545
1984	26.05284
1985	24.38205
1986	23.33608
1987	21.54752
1988	15.49346
1989	10.91745
1990	6.75374
1991	8.97558
1992	10.86726
1993	16.06764
1994	24.74082
1995	24.37361
1996	26.48761
1997	30.17817
1998	31.16589
1999	36.08486
2000	40.59969
2001	49.29728
2002	67.71967
2003	87.25873
2004	106.45938
2005	113.7211
2006	111.6121
2007	135.53928
2008	113.34627
2009	111.06879
2010	103.11133
2011	89.33616
2012	76.51714
2013	69.76246
2014	71.0478
2015	73.78112
2016	79.2946