Year	Percent
1960	17.03757
1961	18.55678
1962	19.62895
1963	19.21199
1964	21.32945
1965	17.81304
1966	17.96322
1967	18.16413
1968	18.68503
1969	17.69887
1970	22.04973
1971	21.05763
1972	19.38406
1973	23.50025
1974	26.80374
1975	25.85061
1976	26.38423
1977	28.37261
1978	27.96757
1979	34.63763
1980	28.86568
1981	22.66132
1982	13.49483
1983	23.54153
1984	24.05303
1985	31.32703
1986	35.37579
1987	36.43248
1988	30.10424
1989	31.40867
1990	27.90682
1991	24.39791
1992	24.81381
1993	29.32389
1994	34.88275
1995	33.76754
1996	29.06652
1997	30.76927
1998	29.56736
1999	32.18975
2000	34.68108
2001	49.65612
2002	113.66087
2003	58.74595
2004	50.75973
2005	37.86947
2006	48.32879
2007	40.22753
2008	37.59516
2009	41.97111
2010	43.5451
2011	41.80382
2012	42.10757
2013	39.08332
2014	42.46516
2015	36.42993
2016	39.67083
2017	39.67972