Period	Percent
1970-01-01	0.66
1975-01-01	0.98
1980-01-01	2.08
1985-01-01	3.00
1990-01-01	3.26
1995-01-01	3.23
2000-01-01	3.34
2005-01-01	2.80
2010-01-01	2.29