Year	Percent
1972	14.87256
1973	15.64207
1974	15.52773
1975	19.78798
1976	16.55255
1977	19.9795
1978	19.50538
1979	20.02643
1980	16.55532
1981	16.89785
1982	17.25773
1983	16.77699
1984	16.55957
1985	15.89648
1986	16.0177
1987	17.19631
1988	18.0625
1989	18.32957
1990	18.67672
1991	18.41542
1992	20.65143
1993	20.2477
1994	18.85494
1995	18.35121
1997	19.40549
1998	19.16525
1999	19.87324
2002	19.07257
2003	18.78977
2004	18.97885
2005	20.97294
2006	21.45102
2007	23.9054
2008	26.49263
2009	23.4563
2010	22.81923
2011	23.29676