This paper establishes sets of sufficient conditions which guarantee that Ramsey prices exceed their corresponding marginal costs. In the literature, it is known that gross substitutabilities between the goods produced by the monopolist tend to raise their markup rates. Therefore, one might conjecture that the gross substitutabilities can guarantee that Ramsey prices exceed their marginal costs. Among others, it is established that the above conjecture holds under additional conditions. 本文旨在建構幾組充分條件以保證藍氏定價(Ramsey price)高於其邊際成本。文獻指出當產品間是粗代替品時，獨占廠商定價傾向於提高其利潤率，所以一般推測粗代替品可以保證藍氏定價高於其邊際成本。本文証明了在某些附加條件之下，上述推測可以成立。
