**Table S1.3.** Effects of the Jordanian Refugee Surge, Polity IV Index

||**OI**<br>|**C all**<br>|**OIC mi**<br>|**nus PAK**<br>|**OIC**<br>|**SAL**<br>|
|---|---|---|---|---|---|---|
||**Effect**<br>**(1)**|**_p_-value**<br>**(2)**|**Effect**<br>**(3)**|**_p_-value**<br>**(4)**|**Effect**<br>**(5)**|**_p_-value**<br>**(6)**|
|1991|3.740|0.545|3.740|0.500|1.930|0.714|
|1992|5.740|0.455|5.740|0.417|3.620|0.714|
|1993|5.110|0.455|5.110|0.417|2.240|0.857|
|1994|5.110|0.455|5.110|0.417|2.240|0.857|
|1995|5.110|0.455|5.110|0.417|2.240|0.857|
|1996|5.110|0.364|5.110|0.500|2.240|0.714|
|1997|5.110|0.545|5.110|0.583|2.240|0.714|
|1998|5.110|0.545|5.110|0.583|1.930|0.571|
|1999|5.110|0.455|5.110|0.333|1.930|0.714|
|2000|3.740|0.545|3.740|0.417|1.930|0.714|
|2001|3.740|0.545|3.740|0.333|1.930|0.714|
|2002|4.055|0.455|4.055|0.333|2.620|0.429|
|2003|4.055|0.455|4.055|0.333|2.620|0.429|
|2004|4.055|0.364|4.055|0.250|2.620|0.429|
|2005|4.055|0.364|4.055|0.250|2.620|0.429|
|2006|4.055|0.364|4.055|0.250|2.620|0.429|
|2007|3.055|0.545|3.055|0.417|1.620|0.571|
|2008|3.055|0.455|3.055|0.417|1.620|0.571|
|2009|3.055|0.545|3.055|0.667|1.620|0.714|
|2010|3.055|0.545|3.055|0.583|1.620|0.571|
|2011|0.535|0.909|0.535|0.917|−4.520|0.429|
|2012|1.590|0.818|1.590|0.917|−5.210|0.429|
|2013|1.275|0.545|1.275|0.750|−5.900|0.286|
|2014|0.960|0.909|0.960|0.750|−6.590|0.286|
|2015|0.960|0.909|0.960|0.750|−6.590|0.286|

_Source_ : Authors’ analysis of the Polity IV index. Additional data come from the Polity IV dataset, Freedom House, the Database of Political Institutions (DPI), and the JuriGlobe database. _Note_ : Estimated treatment effects on Jordan’s Polity IV score and corresponding permutation test _p_ -values that indicate the fraction of estimated treatment effects that are larger than the estimated effect on Jordan’s Polity IV score following the 1990 refugee surge. OIC denotes the full Organisation of Islamic Cooperation donor pool; OIC minus PAK denotes the OIC donor without Pakistan; and OIC SAL denotes the donor pool limited to OIC countries that received Structural Adjustment Loans (SALs) from either the World Bank or International Monetary Fund (IMF).

**Table S1.4.** Goodness of Fit Estimates for Synthetic Jordan, Polity IV Index

||**OIC all**|**OIC minus PAK**|**OIC SAL**|
|---|---|---|---|
|_Pre-treatment fit_||||
|(1) RMSPE|1.382|1.382|1.822|
|_Permutation tests_||||
|(2) Pr(post RMSPE≥Jordan)|0.909|0.833|1.000|
|(3) Pr(pre/post RMSPE≥Jordan)|0.636|0.667|1.000|
|(4) Pr(pre RMSPE≥Jordan)|0.455|0.417|0.000|

_Source_ : Authors’ analysis of the Polity IV index. Additional data come from the Polity IV dataset, Freedom House, the Database of Political Institutions (DPI), and the JuriGlobe database. _Note_ : Table presents goodness of fit metrics for Synthetic Jordan with the Polity IV index as the outcome of interest. Goodness of fit for Synthetic Jordan is denoted by its Root Mean Squared Prediction Error (RMSPE). Placebo tests reassign the 1990 refugee surge to each control country and report the fraction of countries with a post-treatment RSMPE greater than Jordan’s RMPSE, normalized ratio of pre- to post-treatment RMSPE greater than Jordan’s RMSPE, and pre-treatment RMSPE greater than Jordan’s. OIC denotes the full Organisation of Islamic Cooperation donor pool; OIC minus PAK denotes the OIC donor without Pakistan; and OIC SAL denotes the donor pool limited to OIC countries that received Structural Adjustment Loans (SALs) from either the World Bank or International Monetary Fund (IMF).