地下經濟與金融發展對經濟成長的影響：追蹤資料的實證研究

Abstract

本文旨在研究地下經濟規模與金融發展對實質人均GDP成長率之影響。我們使用二種不同金融發展資料，分別為私部門信貸規模及股市成交值規模。使用的資料型式為追蹤資料，時間由西元1981年至2008年，國家共22個，其中有14個已開發國家，8個開發中國家。模型部分共採用三種型式，首先為一般線性模型，其次為納入地下經濟規模與金融發展交互作用之非線性模型，最後則是門檻迴歸模型。\n\n 結果顯示，在一般線性模型中，地下經濟規模及私部門信貸規模對實質人均GDP成長率的影響並不顯著，而股市成交值規模對實質人均GDP成長率有顯著正面影響。\n\n 而在納入地下經濟規模與金融發展之交互作用項後，私部門信貸規模與地下經濟規模的交互作用項對實質人均GDP成長率有顯著負面影響，而股市成交值規模與地下經濟規模之交互作用項對實質人均GDP成長率有負面影響，但不顯著。由上面的結果，我們推斷地下經濟規模與實質人均GDP成長率可能存在著非線性的關係。\n\n 在門檻迴歸中，若把顯著水準設在10%，我們發現納入私部門信貸規模與股市成交值規模的模型存在顯著的門檻效果。在門檻迴歸中，若把私部門信貸規模或是股市成交值規模當作門檻變數，當金融發展程度低時，地下經濟規模對實質人均GDP成長率有顯著正面影響，而當金融發展程度高時，地下經濟規模對實質人均GDP成長率的影響並不顯著。\n\n 總結來說，我們建議低度金融發展國家適度的允許地下部門發展，因為政府無法干預地下部門，因此地下部門的營運較有效率，適度允許反而有助於提高資本投資的效率，進而促進實質人均GDP成長率。相反地，我們建議高度金融發展國家的政府應限制地下部門的發展。

This paper focuses on linear effects and nonlinear effects of underground economy and financial development on the growth rate of real GDP per capita. Utilizing two alternative measures of financial development, including the size of private credit and stock trade. The analysis relies on a sample of 22 countries for the period 1981-2008, including 14 developed countries and 8 developing countries. We use three different models, including linear model, nonlinear regression with a cross-term and panel threshold model.\n\n The results show that in the linear model, underground economy and private credit have no significant impact on the growth rate of real GDP per capita, but stock trade has a significant positive impact on the growth rate of real GDP per capita. \n\n Moreover, the interaction between private credit and underground economy has a significant negative impact on the growth rate of real GDP per capita, on the other hand, the interaction between stock trade and underground economy has an insignificant negative impact on the growth rate of real GDP per capita. Hence, we speculate there have a nonlinear effect between underground economy and the growth rate of real GDP per capita. \n\n In the panel threshold model, if the level of significance is set in 10%, we find that the model with private credit and stock trade have threshold effect, it implies that the sample can be split into two regimes: High degree of financial development and Low degree of financial development. Underground economy has a significant positive impact on the growth rate of real GDP per capita when private credit is low, so does stock trade. \n\n In conclusion, we suggest that it may be optimal for countries with a less developed formal financial sector to accept more tax evasion, because it accelerates the efficiency in capital investment and then facilates the growth rate of real GDP per capita. On the contrary, countries with a more developed formal financial sector should impose more tax compliance.