The Center for Systemic Peace posted its annual update of the Polity data set on Friday, here. The data set now covers the period 1800–2014.
For those of you who haven’t already fled the page to go download the data and who aren’t political scientists: Polity measures patterns of political authority in all countries with populations larger than 500,000. It is one of the mostly widely used data sets in the fields of comparative politics and international relations. Polity is also tremendously useful in forecasts of rare political crises—partly because it measures some very important things, but also because it is updated every year on a fairly predictable schedule. Thanks to PITF and CSP for that.
I thought I would mark the occasion by visualizing Polity in a new way (for me, at least). In the past, I’ve used heat maps (here and here) and line plots of summary statistics. This time, I wanted to try something other than a heat map that would show change over time in a distribution, instead of just a central tendency. Weakly inspired by the often-imitated cover of Joy Division’s 1979 album, here’s what I got. Each line in this chart is a kernel density plot of one year’s Polity scores, which range from -10 to 10 and are meant to indicate how democratic a country’s politics are. The small number of cases with special codes that don’t fit on this scale (-66, -77, and -88) have been set aside.
The chart shows once again that the world has become much more democratic in the past half-century, with most of those gains occurring in the past 30 years. In the early 1960s, the distribution of national political regimes was bimodal, but authoritarian regimes outnumbering the more-democratic ones. As recently as the early 1970s, most regimes still fell toward the authoritarian end of the scale. Starting in the late 1980s, though, the authoritarian peak eroded quickly, and the balance of the distribution shifted toward the democratic end. Despite continuing talk of a democratic recession, the (political) world in 2014 is still mostly composed of relatively democratic regimes, and this data set doesn’t show much change in that basic pattern over the past decade.
Dart-Throwing Chimp 
prisonrodeo
/ May 11, 2015Pretty cool. I bet if you used a narrower bandwidth for the smoother, it’d be visually even closer (there’s a bit more bumpiness in the album image). Then extend the scale to [-20,20] and Bob’s your uncle.
dartthrowingchimp
/ May 11, 2015Yeah, I should try that, thanks. I first did B&W, too, but I didn’t think it was so hot for web viewing.