The only way to determine whether a man is rich or poor is to examine the amount of work he can afford to buy. "Work is the real exchange of goods."Smith also describes the ratio of cheap years and manufacturing output versus output in estimated years. He argues that while some examples, such as flax production in France, show a correlation, another example in Scotland shows the opposite. He concludes that there are too many variables to make any statement about this.From Stock Earnings: In this chapter, Smith uses interest rates as an indicator of stock earnings. This is because interest can only be paid with earnings from shares, so creditors will be able to increase rates in proportion to the increase or decrease in earnings of their debtors.