The required degree of increasing returns-to-scale to satisfy the Benhabib–Farmer condition for local indeterminacy is too high to be empirically plausible. In the paper, we develop a natural extension of Benhabib and Farmerʼs (1994) model by introducing aggregation increasing returns to variety. It is shown that an increase in the degree of monopoly power can create increasing returns to an expansion in variety which decreases reliance on the degree of increasing returns-to-scale in production for generating local indeterminacy. As the degree of monopoly power increases, the required degree of increasing returns for local indeterminacy decreases monotonically. As a result, our numerical analysis indicates that the required degree of increasing returns for local indeterminacy can be easily located in the empirically plausible range. 關於不確定性均衡之探討，Benhabib and Farrner (1994)一文說明，只有在生產外部性相當大或規模報酬遞增的現象很明顯時，才可能發生。然而，依該文所得之數據，若要發生均衡不確定，所對應的外部性參數值，明顯大於既有文獻的估計而顯得相當不合理。本文發現，於商品市場不完全競爭，且中問商品多樣化對最終財的產出其規模報酬特性時，得以在生產外部性極小的情況下，產生局部不確定的均衡。當中間財廠商的獨占力愈大，規模報酬遞增的效果愈強，發生不確定均衡時所需對應的生產外部性愈小，且對應之外部性參數值，也符合實證估計資料的合理範圍。
