Research Design

Phase I: The Constitutional Chronology

The first phase of our research involved constructing constitutional chronologies for all independent states in our sample. We relied upon a collection of cross-national, regional, and country-level sources in order to compile the data, including Constitutions of the Countries of the World (Flanz and Blaustein 1971-present), Constitutions of the World (Maddex 2001), The Constitutions of the Americas (Fitzgibbon 1948), Constitutions of Nations (Peaslee 1950-1971), the Political Database of the Americas at Georgetown, HeinOnline’s World Constitutions Illustrated, and various country-level studies. We have largely completed the historical chronology, with more than 3500 constitutional events occurring between 1789 and the present. While we are confident that we have identified nearly all of the “new” constitutions in our sample, we are not so certain of amendments to these documents, which are typically less well-documented. However, we continue to update the chronology as we become aware of historical amendments, and we continually add new events as they occur. You can explore the full chronology on our Timeline of Constitutions page.

The remainder of this page provides information about a number of decisions we made when creating the constitutional chronology.

Conceptualizing Constitutions

Section of the CCP chronology

Section of the CCP chronology

A crucial, and not at all trivial, step in building the chronology was to identify what constitutes a country’s “constitution” at any given time. The vast majority of countries have discrete documents that are clearly recognized as constitutions, but some countries (e.g. Saudi Arabia until 1992) have unwritten constitutions and others (e.g. New Zealand, Israel) utilize a collection of documents that scholars consider too important to not be a constitution. In order to delineate the concept of a constitution and its relationship with written documents, we identified constitutions by appealing to three conditions, any one of which is sufficient to qualify the document as a constitution. Constitutions are those documents that either:

1. are identified explicitly as the “Constitution,” “Fundamental Law,” or “Basic Law” of a country;

2. contain explicit provisions that establish the contents as highest law, either because they are entrenched or limit future law; or

3. change the basic pattern of authority by establishing or suspending an executive or legislative branch of government

These rather bright-line rules provide a fairly straightforward classification of documents that, upon implementation, appears to have face validity.

Uncodified and Quasi-Constitutions

A special problem concerns the small number of countries that either lack written constitutions or have written quasi-constitutions composed of a number of politically entrenched laws. Our focus on written constitutions forces us to exclude countries without any written constitution whatsoever. For those countries that have only quasi-constitutions composed of one or more pieces of legislation, we searched for scholarly consensus from area specialists on exactly which documents are to be considered constitutional. For example, we now include a set of constitutionally-relevant statutes for the United Kingdom’s constitution, relying on the definition provided by University College London’s Constitution Unit. Fortunately, at least for analytic purposes, formal constitutions are the norm and defining a state’s constitution is largely straightforward. Nevertheless, we should be clear that the dataset includes some “complicated” cases, for which we seek to provide clear interpretive guidance concerning exactly which documents were coded.

Unit of Analysis

The unit of analysis in this study is the country-year. Specifically, each unit is defined as the written constitution in force on December 31 of a given year for a given country. For example, constitutional amendments to Brazil’s constitution that were promulgated in August 2004 would be included in the case “Brazil 2004.” Theoretically, this definition implies a universe of n countries by t years. In practice, the universe is populated by only those country-years in which the constitution has changed, changes we call “constitutional events.” Although the dataset includes only these country-years, one could easily construct an uninterrupted time series by carrying past scores forward to interpolate years between events. As such, our framework is easily adaptable for those analysts interested in identifying the provisions that are in force in a given year.


In developing our sample, we established sampling guidelines with respect to two dimensions:

Time — We include constitutional events from 1789 to present. The year 1789 marks the effective date of the United States constitution, the widely reputed “first” document of its kind. While other documents of quasi-constitutional status predate the US document (e.g., Magna Carta), such documents are sufficiently rare and ambiguously “constitutional” that 1789 makes for an appropriate and practical beginning for our study.

Countries — Our intention is to include all independent states that have existed for at least five years during the sampled time frame. We base our sample of states on Ward and Gleditsch’s (2006) list of states (including microstates), except where otherwise noted. We do not, however, include constitutions of subnational units in federal systems.

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