Period	Percent
1970-01-01	4.60
1975-01-01	6.60
1980-01-01	10.10
1985-01-01	12.70
1990-01-01	12.74
1995-01-01	13.18
2000-01-01	10.34
2005-01-01	8.30
2010-01-01	8.28