Year	Percent
1977	6.91378
1978	9.55977
1979	10.35471
1980	13.33444
1981	16.58986
1982	21.50915
1983	19.04235
1984	20.41021
1985	30.22535
1986	26.11486
1987	30.78209
1988	29.10292
1989	17.28614
1990	20.5243
1991	17.64294
1992	16.5118
1993	24.56573
1994	21.30079
1995	21.00664
1996	20.08528
1997	20.27071
1998	21.15319
1999	24.80258
2000	20.78252
2001	11.93716
2002	11.56254
2003	13.48954
2004	15.51736
2005	19.13225
2006	10.06267
2007	7.60419
2008	5.92471
2009	7.38879
2010	3.55359
2011	4.32602
2012	3.12848
2013	2.54081
2014	4.99419
2015	6.26659