本文建立一個包含有金融雙元體系的內生成長模型，以探究政府的最適逃漏稅稽查政策。模型中，人們可透過正式的金融體系或非正式金融體系累積資本，並且由非正式金融體小所獲得的資本所得可以逃漏稅但由正式金融體小所獲得的資本所得無法逃漏稅。延續結構學派的看法，我們發現適度的允許資本逃漏稅對開發中國家而言是一個最適的政策。相反的，已開發國家政府應政力減少逃漏稅。此外逃漏稅愈嚴重，地下金融體系規模就愈大。因此，本文發現開發中國家，相對於已開發國家，有較嚴重的逃漏稅及較大規模的地下金融體系。最後，本研究的模擬分析也發現，具有較嚴重逃漏稅及較大規模的地下金融體系國家，其經濟成長表現可以和逃漏稅較不嚴重國家及地下金融體小較的國家相類似。這個結果與1980年代和1990年代亞洲四小龍的經濟成長經驗相符合。

This paper examines the optimal policy of tax enforcement in an endogenous growth model with the presence of financial dualism. Individuals can accumulate capital by depositing savings into the formal and informal financial sectors, and capital incomes derived via informal (formal) financial institutions are evadable (non-evadable). By following the argument of new structuralists, we find that it may be optimal for countries with a less developed formal financial sector to choose a policy of tax enforcement that results in more severe tax evasion and a larger informal financial sector. Conversely, countries with a more developed formal financial sector should impose a policy of tax enforcement that leads to more tax compliance and a small size of the informal financial sector. This result is consistent with recent empirical studies. Moreover, our calibration shows that countries with a less developed financial sector and more severe tax evasion can perform equally well in terms of economic growth with those countries whose financial sector is more developed and tax evasion is less severe. This may provide a theoretical explanation for the growth experience of Asian tigers in the 1980s and 1990s.