Period	Percent
1970-01-01	0.09
1975-01-01	0.10
1980-01-01	0.19
1985-01-01	0.48
1990-01-01	0.72
1995-01-01	0.97
2000-01-01	1.30
2005-01-01	1.77
2010-01-01	1.89