Edwards and Bell suggested that with only slight changes in present accounting procedures, four types of income can be isolated:

1. Current operating profit: the excess of sales revenues over the current cost of inputs used in production and sold

2. Realizable cost savings: the increases in the prices of assets held during the period

3. Realized cost savings: the difference between historical costs and the current purchase price of goods sold

4. Realized capital gains: the excess of sales proceeds over historical costs on the disposal of long-term assets

Which of the four types is most useful for creditors and why?