Period	Percent
1970-01-01	10.49
1975-01-01	11.74
1980-01-01	12.75
1985-01-01	13.30
1990-01-01	13.16
1995-01-01	13.94
2000-01-01	16.28
2005-01-01	20.00
2010-01-01	18.80