Period	Percent
1970-01-01	0.94
1975-01-01	1.70
1980-01-01	2.40
1985-01-01	3.27
1990-01-01	2.78
1995-01-01	2.05
2000-01-01	1.27
2005-01-01	0.03
2010-01-01	1.27