The age of democracies is calculated based on data published by Boix, Miller, and Rosato (2018) on political regimes from 1800 through to 2015. Here we rely on Version 3.0 of Boix, Miller, and Rosato's dataset which was published in March 2018. The original version of their data was published in 2012.

Full citation: "Boix, C., Miller, M., & Rosato, S. (2013). A complete data set of political regimes, 1800–2007. Comparative Political Studies, 46(12), 1523–1554." Boix et al. determine the political regime of each country from 1800 through to 2015.

They define a country as democratic if it meets the following conditions for both contestation and participation.

"Contestation:

1. The executive is directly or indirectly elected in popular elections and is responsible either directly to voters or to a legislature.

2. The legislature (or the executive if elected directly) is chosen in free and fair elections.

Participation:

3. A majority of adult men has the right to vote."

The age of democracies through to 2015 can then be calculated as the number of years a country has been defined as democratic. For example, Canada has been defined as a democracy for 149 years because it was coded as a democracy from 1867 to 2015.

Note: The oldest democracy (the US) is listed as having been 216 years old at the end of 2015 only because Boix, Miller, and Rosato's dataset only extends to 1800. It would be more correct to state that democracy in the US is at least 216 years old.

Sources

Data Published By: Boix, C., Miller, M., & Rosato, S. (2013), "A complete data set of political regimes, 1800–2007", Comparative Political Studies, 46(12), 1523–1554; and Boix-Miller-Rosato (BMR) Dichotomous Coding of Democracy, Version 3.0 (March 2018)

Data publisher source:See description.

Link: https://sites.google.com/site/mkmtwo/data