Year	Percent
1970-01-01	13.86608537
1971-01-01	13.74316877
1972-01-01	16.55070160
1973-01-01	18.08183073
1974-01-01	23.82127174
1975-01-01	24.80245876
1976-01-01	29.05725463
1977-01-01	28.65091405
1978-01-01	24.72603280
1979-01-01	17.31172505
1980-01-01	20.13068647
1981-01-01	23.24700099
1982-01-01	19.97407280
1983-01-01	11.33996090
1984-01-01	8.37984024
1985-01-01	10.01259122
1986-01-01	15.08915409
1987-01-01	17.90309908
1988-01-01	11.46091130
1989-01-01	15.05218208
1990-01-01	15.48034229
1991-01-01	15.86454551
1992-01-01	16.96599986
1993-01-01	19.46589377
1994-01-01	37.05075832
1995-01-01	41.54555283
1996-01-01	28.72274911
1997-01-01	23.27641015
1998-01-01	17.23756106
1999-01-01	69.03732338
2000-01-01	62.75007325
2001-01-01	62.07033825
2002-01-01	74.65436750
2003-01-01	69.19097757
2004-01-01	82.96230119
2005-01-01	80.78136921
2006-01-01	65.98377795
2007-01-01	71.69732223
2008-01-01	72.39092497
2009-01-01	72.73254961
2010-01-01	67.16144264