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Content warning: Frequentist statistics

While economics is often derided as the dismal science, I believe that economists have done much to improve policymaking in the world. Their models are never perfect, but they are often useful. I find that Political Science as a field has been less successful at producing utility, as evidenced by our more tenuous relationship with policymaking.

Firstly, political scientists (poli sci's) have a more difficult subject matter: case numbers are usually small, strategies are constantly changing, and the room where it happens is often intentionally barred to researchers. Secondly, Poli Sci's have a more diverse set of normative missions, and no consensus on revealed preference. Thirdly, usefulness often depends on predicting highly uncertain events, but calibration and decision theory are omitted from the traditional training.

The purpose of this blog series is to recognize poli sci's who's work has high consequentialist value. I admire these writers for not just satisfying academic incentives but writing articles with real potential to improve the lives of their fellow man. They are my role models.

Are Parliamentary Systems Better? by Gerring, Thacker and Moreno

The largest differences between the democracies of the world are the unity of legistlature and the executive, the number of veto positions, the form of election, and federal vs. unitary states. When countries form or democratize constitution writers must make difficult, uncertain choices on these axis. Gerring et al. compare the outcomes caused by presidential systems and parliamentary systems. They skip labyrinthine debates about the risks and advantages of each design by looking directly at the outcomes through a massive regression analysis.

Under presidentialism, legislature and executive are elected separately. Each have a mandate from the people and they often disagree about policy, resulting in gridlock. Americans will be familiar with this problem. But the multiple elected parties can also "check and balance" one another, which might result in more stable economic policy. Under parliamentary systems the legislature chooses the prime minister directly. A majority of members of parliament are free to replace the prime minister at any time by a no confidence vote. The government cannot be split and there are fewer veto points. Broadly speaking, presidentialism is common in Latin American, the US and Africa. Parliamentalism is common in Europe, South Asia, East Asia and British colonies.

The great innovation of Gerring and Tacker is to measure outcomes with not one but 14 separate measure of government outcomes. The challenge to the regression is that so many different factors (culture, political traditions, starting gdp, malaria, democracy, legal origin, resource curse) affect outcomes that identifying the parliamentalism effect is fraught. They solve this with 14 outcomes including GDPPC, telephone mainlines, trade openness, investment ratings, corruption indices, bureaucratic quality indices, and illiteracy.

The results find that parliamentary government leaders to better outcomes. They find statistically distinguishable positive effect on 7 of 14 governance outcomes and no negative effects. The most plausible mechanism is that unitary governments are better at solving collective action problems. I also suspect that parliaments are easier for voters to understand and thus punish bad governance (split systems allow the party holding each branch to blame the other, confusing voters). These affects seem stronger than the hypothesised benefits of presidentialism (see federalist papers, etc.)

Gerring et al. certainly don't have the last word on these issues, future regressions have argued the real effect is smaller. But the decision to use many dependent variables greatly improves their robustness. Furthermore no subsequent article (afaik) has found evidence supporting presidentialism. So if one is writing a constitution, choosing parliamentalism is smart unless you have a massive prior for presidentialism.

It hardly needs saying that the longterm value of a better constitution is massive.





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While economics is often derided as the dismal science, I believe that economists have done much to improve policymaking in the world.

In keeping with the abolitionists origins of the phrase:

Carlyle’s target was ... economists such as John Stuart Mill, who argued that it was institutions, not race, that explained why some nations were rich and others poor. Carlyle attacked Mill ... for supporting the emancipation of slaves. It was this fact—that economics assumed that people were basically all the same, and thus all entitled to liberty—that led Carlyle to label economics “the dismal science.”

Thanks a lot for this! I've vaguely had the cached intuition that "political scientists think parliamentary systems are better" but never dug into it myself, very glad that you spelled out the research clearly + highlighted its importance, in a way that's easy to understand.

You say:

So if one is writing a constitution, choosing parliamentalism is smart unless you have a massive prior for presidentialism.
It hardly needs saying that the longterm value of a better constitution is massive.

Are you aware of any constitutional designers that took inspiration from this paper? If not, do you think future constitutional designers are likely to?

It appears that South Sudan has a presidential system.

Good question. The key is that Gerring's paper ADJUSTED FOR DEMOCRACY. So it really means that "parliaments are better when they successfully become democracies", not "parliaments are better in general". This is a big stupid on Gerring's part. I just noticed it and am mad. Anyway-

South Sudan becoming a democracy was very hard due to the proto-state institutions before independence. Ethno-nationalist patrimonial warlord autocracies dominated pre-independence South Sudan and had effectively won their independence in a long and bloody civil war. And there were two warlordships of similar power and ethnic bases (and polygamy). Describing the main factions can get long and complicated and I could easily make a mistake. I'll just talk about three groups, the majority SPLM faction (mostly Dinka), the minority SPLM faction (mostly Nuer) and the International Community. I'm not an expert, so consider this a guess.

For the head of the majority faction (Salva Kiir) presidentialism is good because it concentrates power and patronage opportunities in his hands. He wants the presidency to have strong independence from the legislature. Remember the legislature is full of his lackeys. Being subservient to 300 lackeys makes corruption hard; capable people sneak in and bribes are more expensive (See Bueno De Mesquita, selectorate theory). This is the main reason, IMO.

For the head of the minority faction (Riek Machar), presidentialism also sounds nice because the upper house represented provincial governments. So the Nuer-dominated provinces have institutionalized power, maybe a veto. Note that war broke out a few months after Salva Kiir fired his ministers to consolidate power.

For the international community, the main thing is making sure that the government splits the money fairly. They know that state capacity will be tiny. In practice, they will be providing the services. But as long as the majority and minority faction are sharing the windfalls into their respective pyramid schemes fairly, a civil war might not happen. The massive corruption must seem fair to each warlord. Presidentialism should make this easier as well (checks and balances, multiple state actors with their own mandate).

If these actors were maximizing the quality of the health ministry in 20 years, Gerring would have been relevant. But none of them were.

Thanks again! I'm also still interested on whether you have thoughts on whether future constitutional designers are likely to take inspiration from this paper.

I don't know yet. I am curious.

Thanks a lot for this comment. This was detailed, informative and I learned a lot about the situation in South Sudan.

For those interested in the topic, political scientist Lee Drutman’s new book “Breaking the Two-Party Doom Loop: The Case for Multiparty Democracy in America” may serve as a good contemporary, but less quantitative, introduction.

Drutman is bae.

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Epistemic status: have not read the paper

The conclusion seems reasonable, but I have some concerns about taking this at face value. The large number of dependent variables also makes me a bit skeptical. How do we know they weren't p-hacking by, say, choosing the best 14 of 25 possible dependent variables? More importantly, it doesn't seem to robustly establish causation. What if Latin America, the US and Africa have worse outcomes due to lack of trade or something?

Furthermore no subsequent article (afaik) has found evidence supporting presidentialism.

How many such articles have there been?

Good questions Thomas. The point of the blog series is to highlight papers that ask the right questions and use the right methods to have consequentialist value. I am not arguing that the Gerring paper is the last word. I'll answer a few of your questions, though.

  1. We know they aren't p-hacking in the selection of dependent variables because there are very few such variables that cover every country-year of interest. How many organizations measured the governance quality of Liberia, Columbia and Denmark in 1953. I'm working on introducing a new one using weather station quality.

  2. I didn't want to dive into the regression table in my blog post. All models used adjust for continent. They also adjust for distance to financial center. I would also point out that if the continents with lots of presidential regimes have less cross-border trade, this is evidence against quality of governance of presidentialism.

  3. There is a later study with an expanded dataset that supported the null on GDP, but I didn't include it because it ignored the 13 other governance indicators. This isn't my main research area so I won't do a full literature review for this blog post. In municipalities the same result is robustly observed.

If robustly establishing causation means "adjusting for every factor which could possibly affect governance outcomes at the country level", then the question is clearly unanswerable. There are hundreds of such factors and RCT's are impossible. But as consequentialists our goal isn't to achieve some arbitrary degree of confidence in our beliefs. The goal is to make better decisions. Since your prior on pres v. parl should be near .5, this evidence compellingly moves us toward the parl side, maybe to .7 . For a constitutional designer, that's a hugely valuable update. There remains a 30% chance of making the wrong decision, but that's way better than a 50% chance of making the wrong decision. Therefore if even one constitutional designer reads this paper, the QALY's that Gerring et al. have made is huge.

Thanks for the elaboration! I'm just glad to hear that the researchers didn't make any obvious mistakes.

It seems like whether we should push for something to be included in a constitution (or any other significant intervention) depends not only on whether the change is good, but also how large the expected effect size is. Am I reading the tables correctly that the effect size of Parliamentarism, while robustly positive, is tiny relative to other factors that contribute to the various R^2s in the models? 

Great question! That is an incorrect interpretation, but this is the fault of the authors for their terrible reporting of the results not maintaining their reproduction data. I noticed the problems after writing.

Basically, those coefficients are the effect of one more year of parliamentarism in your history. So the .004 coefficient on corruption control means that 100 years of parliamentarism (1901-2001) is associated with a .4 increase.

I would also note that the dummy factors are stacked against parliamentarism. Think of it this way. In around 1880, Europe. East Asia and the Commonwealth chose parliamentarism while Latin America, the Francophone countries and (later) Africa chose presidentialism. We can't know if parl is the reason governance is worse in the later group, so we assume the reason is something else. But this is a strong assumption, we cannot rerun history and give the Norwejian constitution to Chile. So you should update up a bit toward parliamentarism.

To take import duties for example. If you keep country dummies in, 50 years of parl is associated with a 2.5% decrease in duties, half the impact of being a democracy. If you remove the continent dummies, then 50 years of parl is about as good as being a democracy.

Generally I would multiply the effect of parl by 50 then compare it to gdp per capita to ballpark total effect.

FWIW, here's a Vox article arguing that gridlock from presidential systems isn't just bad in terms of "normal" policy outcomes, but can also lead to crises of legitimacy if polarization is too high (in which case the executive and legislative branches may both claim to speak for the people while disagreeing, and democratic principles won't necessarily say how to resolve the disagreement), which runs the risk of collapsing the entire political system:


My professor Hans Noel is featured in the article. Nice.

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