American firms used to be allowed to amortise goodwill over many years .

过去美国的企业被允许将商誉在很多年内逐步摊销。

In america these funds , unlike most mutual funds , may amortise their investments so as to round their net asset value ( nav ) to a stable $ 1 per share .

和其它大多数共同基金不同的是，在美国货币市场基金可能会摊薄投资，从而将每一份额的净资产（nav）稳定在1美元。