Labour law can be established both by statutory law and by collective bargaining. How much value does the latter effectively add? In this paper we propose a methodology to address this question: we compare the specific contents of collective agreements (except minimum wages) to their equivalent norms set by statutory law (if any). We illustrate this approach by analysing in detail over 400 norms from six collective agreements in Portugal and then comparing them to the country’s Labour Code. We find that as many as 59 % of those collective bargaining norms are exactly or virtually equal to the Labour Code; only 27 % (an average of 16 norms per convention) are more favourable for the worker; and 11 % (8) are more favourable for the employer. We conclude that collective bargaining in Portugal has a relatively small role as an effective source of labour law. We also present several potential explanations for our findings, including the wide range of statutory law.

劳动法既可以通过成文法也可以通过集体谈判来确立。后者有效地增加了多少价值？在本文中，我们提出了一个方法来解决这个问题：我们将集体协议的具体内容（最低工资除外）与成文法所规定的等价规范进行了比较。我们通过详细分析葡萄牙的六个集体协议中的400多个规范，然后将其与该国的《劳动法》进行比较，来说明这种方法。我们发现，这些集体谈判规范中有多达59％与《劳动法》完全或几乎相同。只有27％（每个公约平均16条规范）对工人更有利；11％（8）对雇主更有利。我们得出的结论是，葡萄牙的集体谈判作为劳动法的有效来源发挥的作用相对较小。我们还为我们的调查结果提供了几种可能的解释，包括广泛的成文法。