Period	Percent
1970-01-01	1.47
1975-01-01	1.43
1980-01-01	1.44
1985-01-01	4.20
1990-01-01	7.33
1995-01-01	8.47
2000-01-01	8.33
2005-01-01	11.98
2010-01-01	16.37