What Variables Define a Legal System?

One issue that I just briefly mentioned in my last post is the choice of variables that help classify legal systems. In statistics, a variable is a measurable attribute for a sub-category of an entity. Variables should be intrinsically different from each other. Together, all variables should constitute a comprehensive representation of the entity as a whole. Continue reading What Variables Define a Legal System?

My Comments on “A Network-Based Taxonomy of the World’s Legal Systems” by Mathias Siems

Despite the (partially) fierce criticism of a quantitative approach to comparative law, the use of statistics to answer comparative law questions seems to have inspired some new comparative law research. A working paper by Mathias Siems with the title A Network-Based Taxonomy of the World’s Legal Systems uses statistics in order to “develop a difference-based taxonomy in accordance with the idea of legal families.” (p. 10)

After discussing pros and cons of classifications in comparative law, Siems comes up with three groups of four variables ranging from “English as official language” to “Paid annual leave.” He then applies these variables to a dataset of 157 countries in order to determine the difference of each single variable with the same variable for each of the remaining countries. This allows him to plot a histogram for  the distribution of the country differences which in turn allows him to create and graphically represent cluster for all the 157 countries studied. Siems subsequently applies his variables to the legal origins literature concluding – somehow surprisingly – that his “network data does not support the legal origins taxonomy.” (p. 17) The last part of the paper is dedicated to developing an alternative classification of the legal systems of the world. By playing with numbers, Siems comes up with four groups: “The Global Anglosphere”, “The Modern European Legal Culture”, “The Rule by Law or Religion” and the “Weak Law in Transition”.

With his paper, Siems opens an interesting avenue for comparative law research. Statistics in general and network analysis in particular may play a role in helping to answer sometimes longstanding questions in comparative law. Yet, statistics are not inherently objective and they need to be properly applied in order to make use of their full potential. In this regard, Siems’ paper raises several concerns. First, the choice of variables by Siems – while well elaborated though probably extendable from a legal standpoint – is problematic from a statistical viewpoint as he mixes categorical variables (here questions with yes/no answers, e.g. “Islam state religion”) with ordinal (or numerical) ones (where the answer lies on a spectrum, e.g. “literacy rate”). Also, the exact translation of the variables into numbers is not really explained. Second, Siems does not really elaborate on the reasoning behind the thresholds (“cut-offs”) for his clusters. Some representations are based on a 0.11 threshold, others on 0.13. Why these thresholds were chosen remains unclear. Third, the conclusion that the classification of the legal systems according to their legal origins is wrong rests on shaky statistics. Little details are given as to the numbers and the reasoning seems somehow circular. Fourth, Siems selects the number of groups into which legal systems can be divided randomly by playing with different numbers and looking which number of groups makes more sense. This, of course, takes away a lot of objectivity from the study.

Overall, the general idea behind A Network-Based Taxonomy of the World’s Legal Systems by Mathias Siems, i.e. to examine traditional issues of comparative law is very innovative and may potentially shape future comparative law research. As any pioneering work it inevitably faces some challenges – mostly due to the fact that the statistical analysis of networks is complex and at the same time so foreign to the conventional way to think about law.


Mathias Siems, A Network-Based Taxonomy of the World’s Legal Systems, 2014 Working Paper Durham Law School, available here.

Can Legal Origins Help Classify the Legal Systems of the World?

Quantitative comparative law rests on four main premises: (1) Legal systems are different; (2) Differences can be traced back to legal origins – the civil law tradition and the common law tradition; (3) Legal rules differ due to historically rooted differences in policies: market support (common law) versus policy implementation (civil law); (4) Legal differences can be quantified. Thus, in quantitative comparative law, legal origins play a crucial role for a country’s political orientation and, hence, economic success. Yet, what does the legal origins theory really entail? It is essentially based on the premise that the legal systems of the world can be traced back to two main sources (or origins): the English common law and the French civil law. (German and Scandinavian civil law are dealt with separately within the civil law group, but most of the publications essentially focus on the dichotomy between English common law and French civil law). Through colonization, conquest and adoption, common and civil law have spread throughout the world and have since shaped our legal environment up to a point where legal origins determine economic success.

To comparative lawyers such a simplistic approach to the legal systems of the world is quite provocative. Two major points of critique have been raised against the legal origins theory. First, the factitiousness of clustering legal systems into groups has been pointed out. As discussed previously, comparative law has started to focus on cultural variability of legal systems. Quantitative comparative law, however, explicitly ignores such cultural nuances in order to focus on big picture differences of laws. Both are, however, just two contrarian approaches to comparative law. In fact, the (artificial) clustering of legal systems into families has a long-standing tradition in comparative legal research and seems to be a legitimate way to facilitate large(r)-scale comparisons. Second, some have pointed out the iffiness of seeing legal origins as the main reason for differences in legal process and economic success. These critics say that legal origins or colonial history are only one of many aspects where the colonial powers diverged. More importantly, colonies also differed in climate and natural resources with the French colonies often on the poorer side. Hence, it is difficult to base economic success on legal origins alone.


  • Daniel Klerman et al, Legal Origin or Colonial History?, 3 J. LEGAL ANALYSIS 379-409 (2011).
  • Rafael La Porta et al., The Economic Consequences of Legal Origins, 46 J. ECON. LIT. 285-332 (2008).
  • Mathias Siems, Reconciling Law & Finance and Comparative Law, 52 M.GILL L J 56-81 (2007).