生產外部性的存在將產生信念自我實現的景氣波動，而這個現象賦予穩定政策一個討論的空間。在一個傳統的Benhabib-Farmer-Guo單部門模型，累進稅被視為一項自動安定機制，可以消除景氣循環的波動；然而，在一個實質景氣循環的兩部門模型底下，反而是累退稅才能使經濟體系達到安定。本文試圖提供另一項政策－所得稅與消費稅組合－以穩定自我信念驅動所造成的景氣波動。透過數值分析，我們顯示政府可以透過降低所得稅並提高消費稅的方式穩定經濟體系。這樣的結論不僅適用於兩部門具有部門特定外部性的情況，且在存在總合外部性的單部門模型也依然適用。

Productivity externalities create room for Keynesian-type stabilization to insulate the economy from belief-driven fluctuations. Conventional wisdomindicates that in a Benhabib-Farmer-Guo one-sector model, a progressive tax schedule operates like an automatic stabilizer that mitigates business cycle fluctuations, but in an indeterminate two-sector real business cycle model a regressive, rather than a progressive, tax policy stabilizes the economy against sunspot-driven fluctuations. This paper proposes an alternative policy - an income tax-cum-consumption tax schedule-to stabilize the economy against sunspot fluctuations. We show numerically that the government can suppress belief-driven fluctuations by implementing a tax switch decreasing the income tax and increasing the consumption tax. This result is robust not only in a two-sector model with sector-specific externalities, but also in a one-sector model with aggregate productivity externalities.