這篇文章主要分析有網路外部性的的情況下，獨佔軟體廠商面對終端使用者盜版(end-user piracy)所受到的影響。假設消費者之間有所得差異及「有限負債(limited liability)」條件。其中「有限負債」會使消費者的盜版成本隨所得增加，因此獨佔廠商可以去利用低所得消費者所帶來網路效果，轉而對高所得消費者定高價以獲得高利潤，尤其是當廠商能有效防止高所得消費者得到網路效果外溢時。當智慧財產權政策趨於愈嚴格執行，則獨佔廠商愈能避免這效果外溢，否則情況會變成每一高所得消費者都獲利，唯獨廠商受害。這是因為邊際消費者受到「有限負債」保護，提高罰金對這些人的均衡狀態絲毫無作用。 關於軟體價格與廠商利潤，一如預期地，這兩個均衡會隨罰金大小或盜版被抓到的機率增加而增加。相反地，由於存在網路效果，上述均衡隨取得盜版成本增加而減少。另外，關於盜版軟體數量，如所預期般，會隨取得盜版成本增加而減少，但出乎意料地，它會隨罰金增加而增加。這是因為提高罰金會促使獨佔廠商更進一步提高軟體價格。同樣的，除非被抓到盜版的機率很高，否則盜版數量會隨這機率增加而增加。另外，如果政策工具執行嚴格，而且政府改將收到的罰金移轉給軟體廠商作為利潤損失的補償，如果目前軟體價格已經很高則這些政策並不會改變任何結果；反之，軟體價格會被更進一步提高。 This paper analyzes the effects of end-user piracy on a monopolized software industry with network effects in which consumers have heterogeneous income and limited liability. Limited liability produces a piracy cost which increases with income. The monopolist thus may be able to exploit the network effect brought about by the piracy of low-income consumers to charge a higher price to high-income consumers thereby earn a higher profit, especially when the monopolist can prevent the network effect from spilling over to the high-income consumers. If intellectual property rights policies are severe enough, then the monopolist can avoid the spillover. Otherwise it may become a case where each high-income buyer benefits from the piracy but the monopolist is hurt. Because the marginal consumer is protected by limited liability, raising the size of the penalty may not have an effect on the equilibrium at all. As expected, the price and the profit always (weakly) increase with either the size of penalty or the detection probability. In contrast, due to the network effect, they may decrease with the cost of obtaining an illegal copy. As expected, the pirated quantity (weakly) decreases with the cost of obtaining an illegal copy. But the pirated quantity always (weakly) increases with the size of the penalty. This is because raising the size of penalty invites the monopolist to raise the price. The pirated quantity similarly increases with the detection probability except when the detection probability is higher than a critical level. If policy instruments are severe enough, giving the penalties to the monopolist instead of the government does not cause any changes because the price is already at its highest possible value; otherwise, the price may be raised.
