Period	Percent
1970-01-01	0.60
1975-01-01	0.42
1980-01-01	0.40
1985-01-01	0.37
1990-01-01	0.36
1995-01-01	1.90
2000-01-01	2.15
2005-01-01	1.86
2010-01-01	1.50