Period	Percent
1970-01-01	1.96
1975-01-01	2.82
1980-01-01	3.95
1985-01-01	5.82
1990-01-01	8.08
1995-01-01	10.42
2000-01-01	10.36
2005-01-01	9.74
2010-01-01	19.76