Period	Percent
1970-01-01	1.18
1975-01-01	1.57
1980-01-01	1.90
1985-01-01	2.21
1990-01-01	2.50
1995-01-01	4.18
2000-01-01	6.89
2005-01-01	6.30
2010-01-01	6.67