What industries were characterized by very high debt ratios?

1. What are the drawbacks to using the interest coverage ratio as a measure of indebtedness?
2. Roughly and on average, what were the liabilities ratios of firms—large and small—on various measures?
3. Did profitable firms have higher or lower indebtedness ratios than unprofitable firms?
4. What industries were characterized by very high debt ratios? Which were characterized by very low debt ratios?