If you have followed the graph-heavy posts in this blog, you may have noticed that I really like the Unified Democracy Scores developed by Daniel Pemstein, Stephen Meserve, and James Melton. The basic idea behind this particular measure of democracy, as they explain in their 2010 article, is as follows. Social scientists have developed a wealth of measures of democracy (some large-scale projects like the Polity dataset or the Freedom in the World index, some small “boutique” efforts by political scientists for a particular research project). Though these measures are typically highly correlated (usually in the 0.8-0.9 range), they still differ significantly for some countries and years. These differences are both conceptual (researchers disagree about the essential characteristics of democracy) and empirical (researchers disagree about whether a given country-year is democratic according to a particular definition).
PMM argue that we can assume that these measures are all getting at a latent trait that is only imperfectly observed and conceptualized by the compilers of all the datasets purporting to measure democracy, and that we can estimate this trait using techniques from item response theory that were originally developed to evaluate the performance of multiple graders in academic settings. They then proceeded to do just that, producing a dataset that not only contains latent variable estimates of democracy for 9850 country-years (200 unique countries), but also estimates of the measurement error associated with these scores (derived from the patterns of disagreement between different democracy measures).
This, to be honest, is one of the main attractions of the UDS for me: I get nervous when I see a measure of democracy that does not have a confidence interval around it, given the empirical and conceptual difficulties involved in producing numerical estimates of a woolly concept like “democracy.” Nevertheless, the UDS had some limitations: for one thing, they only went back to 1946, even though many existing measures of democracy contain information for earlier periods, and PMM never made use of all the publicly available measures of democracy in their construction of the scores, which meant that the standard errors around them were relatively large. (The original UDS used 10 different democracy measures for its construction; the current release uses 12, but I count more than 25).
Moreover, the UDS haven’t been updated since 2014 (and then only to 2012), and PMM seem to have moved on from the project. Pemstein, for example, is now involved with measurement at the V-Dem institute, whose “Varieties of Democracy” dataset promises to be the gold standard for democracy measurement, so I’m guessing the UDS will not receive many more updates, if any. (If you are engaged in serious empirical research on democracy, you should probably be using the V-dem dataset anyway. Seriously, it’s amazing - I may write a post about it later this year). And though in principle one could use PMM's procedure to update these scores, and they even made available an (undocumented) replication package in 2013, I was never able to make their software work properly, and their Bayesian algorithms for estimating the latent trait seemed anyway too computationally intensive for my time and budget.
I think this situation is a pity. For my own purposes – which have to do mostly with the history of political regimes for my current project – I’d like a summary measure of democracy that aggregates both empirical and conceptual uncertainty in a principled way for a very large number of countries, just like I believe the UDS did. But I also would like a measure that goes back as far as possible in time, and is easily updated when new information arises (e.g., there are new releases of Freedom House or Polity). The new V-dem indexes are great on some of these counts (they come with confidence intervals) but not on others (they only cover 2014-1900, they are missing some countries, and the full dataset is a bit unwieldy – too many choices distract me). Other datasets – the trusty Polity dataset, the new and excellent LIED index – do go back to the 19th century, but they provide no estimates of measurement error, and they make specific choices about conceptualization that I do not always agree with.
But why wait for others to create my preferred measure when I can do it myself? So I went ahead and figured out how to first replicate the Unified Democracy scores without using a computationally intensive Bayesian algorithm, and then extended them both forwards to 2015 and backwards to the 19th century (in some cases to the 18th century), using information from 28 different measures of democracy (some of them rather obscure, some just new, like the LIED index or the latest version of the Freedom House data). And I created an R package to let you do the same, should you wish to fiddle with the details of the scores or create your own version of the UDS using different source measures. (Democratizing democracy indexes since 2016!).
The gory details are all in this paper, which explains how to replicate and extend the scores, and contains plenty of diagnostic pictures of the result; but if you only want to see the code to produce the extended UDS scores check out the package vignette here. If you are an R user, you can easily install the package and its documentation by typing (assuming you have devtools installed, and that I’ve done everything correctly on my side):
devtools::install_github(repo = "xmarquez/QuickUDS")
To be sure, for most research projects you probably don’t need this extended Unified Democracy measure. After all, most useful variables in your typical democracy regression are unmeasured or unavailable before the 1950s for most countries, and if your work only requires going back to the 1900s, you are better off with the new V-dem data, rather than this artisanal version of the UDS. But the extended UDS is nice for some things, I think.
First, quantitative history (what I wanted the extended UDS for). For example, consider the problem of measuring democracy in the USA over the entirety of the last two centuries. Existing democracy measures disagree about when the USA first became fully democratic, primarily because they disagree about how much to weigh formal restrictions on women’s suffrage and the formal and informal disenfranchisement of African Americans in their conceptualization. Some measures give the USA the highest possible score early in the 19th century, others after the civil war, others only after 1920, with the introduction of women’s suffrage, and yet others (e.g. LIED) not until 1965, after the Civil Rights Movement. With the extended UDS these differences do not matter very much: as consensus among the different datasets increases, so does the measured US level of democracy:
In the figure above, I use a transformed version of the extended UDS scores whose midpoint is the “consensus” estimate of the cutoff between democracy and non-democracy among minimalist, dichotomous measures in the latent variable scale. (For details, see my paper; the grey areas represent 95% confidence intervals). This version can be interpreted as a probability scale: “1” means the country-year is almost certainly a democracy, “0” means it is almost certainly not a democracy, and “0.5” that it could be either. (Or we could arbitrarily decide that 0-0.33 means the country is likely an autocracy of whatever kind, 0.33-0.66 that it is likely some kind of hybrid regime, and 0.66-1 that is pretty much a democracy, at least by current scholarly standards).
In any case, the extended UDS shows an increase in the USA’s level of democracy in the 1820s (the “Age of Jackson”), the 1870s (after the civil war), the 1920s after female enfranchisement, and a gradual increase in the 1960s after the Civil Rights movement, though the magnitude of each increase (and of the standard error of the resulting score) depends on exactly which measures are used to construct the index. (The spike in the 2000s is an artifact of measurement, having more to do with the fact that lots of datasets end around that time than with any genuine but temporary increase in the USA’s democracy score). Some of these changes would be visible in other datasets, but no other measure would show them all; if you use Polity, for example, you would see a perfect score for the USA since 1871.
Just because what use is this blog if I cannot have a huge vertical visualization, here are ALL THE DEMOCRACY SCORES, alphabetically by country:
(Grey shaded areas represent 95% confidence intervals; blue shaded areas are periods where the country is either deemed to be a member of the system of states in the Gleditsch and Ward list of state system membership since 1816, i.e., independent, or is a microstate in Gleditsch’s tentative list).
A couple of things to note. First, scores are calculated for some countries for periods when they are not generally considered to be independent; this is because some of the underlying data used to produce them (e.g., the V-Dem dataset) produce measures of democracy for existing states when they were under imperial governance (see, e.g., the graphs for India or South Korea).
Second, confidence intervals vary quite a bit, primarily due to the number of measures of democracy available for particular country-years and the degree of their agreement. For some country-years they are so large (because too few datasets bother to produce a measure for a period, or the ones that do disagree radically) that the extended UD score is meaningless, but for most country-years (as I explain in my paper) the standard error of the scores is actually much smaller than the standard error of the “official” UDS, making the measure more useful for empirical research.
Finally, maybe this is just me, but in general the scores tend to capture my intuitions about movements in democracy levels well (which is unsurprising, since they are based on all existing scholarly measures of democracy); see the graphs for Chile or Venezuela, for example. And using these scores we can get a better sense of the magnitude of the historical shifts towards democracy in the last two centuries.
For example, according to the extended UDS (and ignoring measurement uncertainty, just because this is a blog), a good 50% of the world’s population today lives in countries that can be considered basically democratic, but only around 10% live in countries with the highest scores (0.8 and above):
And Huntington’s three waves of democratization are clearly visible in the data (again ignoring measurement uncertainty):
But suppose you are not into quantitative history. There are still a couple of use cases where long-run, quantitative data about democracy with estimates of measurement error is likely to be useful. Consider, for example, the question of the democratic peace, or of the relationship between economic development and democracy – two questions that benefit from very long-run measures of democracy, especially measures that can be easily updated, like this one.
I may write more about this later, but here is an example about a couple of minor things this extended democracy measure might tell us about the basic stylized fact of the “democratic peace.” Using the revised list of interstate wars by Gleditsch, we can create a scatterplot of the mean extended UD score of each side in an interstate war, and calculate the 2-d density distribution of these scores while accounting for their measurement error:
The x- coordinate of each point is the mean extended UD score (in the 0-1 probability scale where 0.5 is the average cutoff between democracy and non-democracy among the most minimalistic measures) of side A in a war listed by Gleditsch; the y-coordinate is the mean extended UD score of side B; each blue square is the 95% “confidence rectangle” around these measures; the shaded blobs are the 2-d probability densities, accounting for measurement error in the scores.
As we can see, the basic stylized fact of a dyadic democratic peace is plausible enough, at least for countries which have a high probability of being democratic. In particular, countries whose mean extended UD democracy score is over 0.8 (in the transformed 0-1 scale) have not fought one another, even after accounting for measurement error. (Though they have fought plenty of wars with other countries, as the plot indicates). But note that the dyadic democratic peace only holds perfectly if we set the cutoff for “being a democracy” quite high (0.8 is in the top 10% of country-years in this large sample; few countries have ever been that democratic); as we go down to the 0.5 cutoff, exceptions accumulate (I’ve labeled some of them).
Anyway, I could go on; if you are interested in this “artisanal” democracy dataset (or in creating your own version of these scores), take a look at the paper, and use the package – and let me know if it works!
(Update 3/25/2016 - some small edits for clarity).
(Update 3/28 - fixed code error).
(Update 3/30 - re-released the code, and updated the graphs, to fix one small mistake with the replication data for the bnr variable).
(Code for this post is available here. Some of it depends on a package I’ve created but not shared yet, so you may not be able to replicate it all.)
This is a really cool extension of one of my favorite data sets from TSCS research. Thanks a bunch for this.
ReplyDeleteThanks Steve!
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