Period	Percent
1970-01-01	0.60
1975-01-01	0.61
1980-01-01	0.50
1985-01-01	1.96
1990-01-01	3.85
1995-01-01	4.04
2000-01-01	4.36
2005-01-01	4.09
2010-01-01	4.10