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.

Drutman is bae.

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.

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.

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