Imagine two types of books. One sells 100,000 copies the first year, 10,000 the second year and 1000 the third. The other kind sells 10,000 copies the first year, 8000 the next, and 7000 the one after that. Which of these two kinds of books would company owners like to have more of?
假設一本書第一年賣十萬本，第二年賣一萬本，第三年賣一千本；跟一本書第一年賣一萬本，第二年賣八千本，第三年還賣七千本，兩者做比較，老闆會希望哪種書多一些？