Year	Percent
1972	16.79227
1973	15.47185
1974	24.99645
1975	20.37713
1980	25.43008
1992	14.69603
1993	11.7353
1994	8.27599
1995	11.24314
1996	11.13103
1997	7.6182
1998	10.90253
1999	7.77134
2001	9.21564
2002	8.36145
2003	8.70277
2004	7.84925
2005	6.24311
2006	5.79083
2007	6.6026
2008	5.94611
2009	8.40495
2010	7.59598
2011	8.85522
2012	9.4287