Period	Percent
1970-01-01	3.80
1975-01-01	5.40
1980-01-01	8.82
1985-01-01	12.35
1990-01-01	15.42
1995-01-01	13.70
2000-01-01	13.21
2005-01-01	10.69
2010-01-01	9.48