Year	Percent
1977	19.05276
1978	21.15851
1980	23.64537
1981	19.65246
1982	21.43401
1983	21.03886
1984	21.4843
1985	17.42041
1986	16.49354
1987	15.78404
1988	12.65276
1989	13.5729
1990	19.90436
1991	17.60191
1992	17.1495
1993	19.0587
1994	19.72345
1995	19.2386
1996	29.14385
1998	24.3905
1999	28.15683
2000	31.06957
2001	33.1198
2002	37.27773
2003	37.68217
2004	47.63747
2005	54.02475
2006	58.71214
2007	59.03637
2008	51.84501
2009	58.23586
2010	58.60012
2012	61.90382
2013	62.46825
2014	63.82447