本文利用因果分析方法(causal analysis)分析台灣2010年實施「3K五級制」外籍產業移工引進新制對整體國內製造業勞工之薪資與雇用影響，並檢視各別職業受影響之程度以了解政策造成之勞工替代與互補效果反映於高低技術勞工的影響。本文資料使用1993年至2019年勞動部「人力運用調查」資料進行實證分析，整理合併資料期間各版本行業及職業標準分類。本文使用的分析方法包括差異中的差異(difference in difference)、合成控制方法(synthetic Control Method)以及交錯型差異中的差異(staggered difference in difference)。
本文發現，整體而言，外籍移工引進對國內勞工之薪資的影響並不顯著，但對雇用人數有顯著之負面影響。進一步，外籍移工對低技術勞工的薪資與雇用有負面影響；在高技術勞工的薪資部分同樣出現負面影響，但是製造業勞工中職業為「主管及經理人員」、「事務支援人員」等職業之雇用人數則有所增加。顯示在高技術勞工確實存在互補效果，但僅發生於雇用人數上，對薪資則否；在低技術勞工上則有替代效果。最後，本文發現在3K五級制後規模較大的工廠雇用了較多的本國勞工，顯示引進外籍移工後造成了本國勞工在不同規模的廠商中的分布有所變化。

This study employs causal analysis to examine the impact of Taiwan's 2010 implementation of the "3K Five-Level System" for the recruitment of foreign industrial migrant workers on the wages and employment of domestic manufacturing workers. It also assesses the varying degrees of impact across different occupations to understand how the policy-induced labor substitution and complementarity effects manifest among high-skilled and low-skilled workers. The data used in this empirical analysis come from the "Manpower Utilization Survey" conducted by Taiwan's Ministry of Labor from 1993 to 2019, with adjustments made to consolidate industry and occupational classification standards across different versions during the data period. The analytical methods employed include Difference-in-Difference (DID), Synthetic Control Method (SCM), and Staggered Difference-in-Difference (Staggered DID).

The findings indicate that, overall, the introduction of foreign migrant workers had no significant impact on the wages of domestic workers but did have a significant negative impact on employment numbers. Further analysis reveals that foreign migrant workers negatively affected the wages and employment of low-skilled workers, while high-skilled workers experienced negative effects on wages as well. However, within the manufacturing sector, occupations such as "managers and administrators" and "clerical support workers" saw an increase in employment numbers. This suggests that complementarity effects for high-skilled workers are evident in terms of employment but not wages, whereas substitution effects are observed for low-skilled workers. Finally, this study finds that after the implementation of the 3K five-level system, larger factories employed more domestic workers, indicating that the introduction of foreign migrant workers led to changes in the distribution of domestic workers across firms of different sizes.

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