Year	Ratio
1971-01-01	0.435620009899139
1972-01-01	0.466349989175797
1973-01-01	0.527790009975433
1974-01-01	0.545639991760254
1975-01-01	0.555410027503967
1976-01-01	0.568929970264435
1977-01-01	0.596430003643036
1978-01-01	0.623059988021851
1979-01-01	0.635580003261566
1980-01-01	0.645759999752045
1981-01-01	0.707199990749359
1982-01-01	0.712930023670197
1984-01-01	0.709909975528717
1985-01-01	0.750670015811920
1986-01-01	0.779349982738495
1987-01-01	0.804279983043671
1988-01-01	0.816079974174500
1989-01-01	0.807089984416962
1990-01-01	0.761990010738373
1992-01-01	0.764680027961731
1996-01-01	0.753359973430634
2002-01-01	0.742389976978302
2003-01-01	0.687390029430389
2004-01-01	0.844219982624054
2012-01-01	0.866010010242462