Period	Percent
1970-01-01	0.22
1975-01-01	0.30
1980-01-01	0.29
1985-01-01	0.36
1990-01-01	0.54
1995-01-01	0.90
2000-01-01	1.31
2005-01-01	1.70
2010-01-01	2.47