Period	Percent
1970-01-01	0.04
1975-01-01	0.00
1980-01-01	0.05
1985-01-01	0.16
1990-01-01	0.47
1995-01-01	0.80
2000-01-01	1.36
2005-01-01	1.92
2010-01-01	2.53