Period	Percent
1970-01-01	6.18
1975-01-01	7.87
1980-01-01	9.46
1985-01-01	11.13
1990-01-01	12.60
1995-01-01	13.67
2000-01-01	16.17
2005-01-01	25.56
2010-01-01	29.29