Period	Percent
1970-01-01	13.21
1975-01-01	14.96
1980-01-01	16.92
1985-01-01	18.11
1990-01-01	18.88
1995-01-01	19.45
2000-01-01	20.36
2005-01-01	19.75
2010-01-01	21.40