Philip Barrett

About Me

I am an Economist at the International Monetary Fund, working in the Research Department.

Research

Working papers

Measuring Social Unrest Using Media Reports (With Maximiliano Appendino, Kate Nguyen, and Jorge de Leon Miranda) IMF Working Paper: July 2020

We present a new index of social unrest based on counts of relevant media reports. The index consists of individual monthly time series for 130 countries, available with almost no lag, and can be easily and transparently replicated. Spikes in the index identify major events, which correspond very closely to event timelines from external sources for four major regional waves of social unrest. We show that the cross-sectional distribution of the index can be simply and precisely characterized, and that social unrest is associated with a 3 percentage point increase in the frequency of social unrest domestically and a 1 percent increase in neighbors in the next six months. Despite this, social unrest is not a better predictor of future social unrest than the country average rate.

Interest-Growth Differentials and Debt Limits in Advanced Economies (submitted) IMF Working Paper: April 2018 Latest version: October 2019 Press coverage: Forbes, Fiscal Times

Do persistently low nominal interest rates mean governments can safely borrow more? I argue standard models of debt sustainability cannot address this issue. The key model parameter in a wide class of models is the long-run difference between the nominal risk-free interest rate and the nominal growth rate. If negative, maximum sustainable debts are unbounded. Data from five advanced economies suggest that this differential is indeed likely negative; different approaches all produce negative point estimates and confidence intervals implying low probabilities of positive values. And even if the long-run differential were positive, the quantitative impact of short-term fluctuations is tiny.

The fiscal cost of conflict: Evidence from Afghanistan 2005-2016 (submitted) IMF Working Paper: September 2018 Latest version: April 2020 Code for Generalized Synthetic Control estimator

I use a monthly panel of provincially-collected central government revenues and conflict fatalities to estimate government revenues lost due to conflict in Afghanistan since 2005. I identify causal effects by instrumenting for conflict using pre-sample ethno-linguistic share. Headline estimates are very large, implying total revenue losses since 2005 of $3bn, and future revenue gains from peace of about 6 percent of GDP per year. Reduced collection efficiency, rather than lower economic activity, appears to be the key channel. OLS estimates understate the causal effect by a factor of four. Comparing to estimates from Powell’s (2017) generalized synthetic control method suggests that this bias results from omitted variables and measurement error in equal share. The findings underscore the considerable economic loss due to conflict, and the importance of careful identification in measuring this loss.

Why are Countries’ Asset Portfolios Exposed to Nominal Exchange Rates? (With Jonathan Adams, revise & resubmit) IMF Working Paper: December 2017 Latest version: September 2018

Most countries hold large gross asset positions, lending in their domestic currency and borrowing in foreign currency. As a result, their balance sheets are exposed to nominal exchange rate movements. We argue that when asset markets are incomplete, this exposure provides partial insurance against shocks that move exchange rates. We demonstrate that this insurance motive can simultaneously generate realistic gross asset positions and resolve the Backus-Smith puzzle: that countries’ relative consumption and real exchange rates are negatively correlated. Local perturbation methods are inaccurate in this setting as they approximate around the wrong interest rate, even when they correctly characterize the average portfolio holdings. So to accurately solve the equilibrium portfolio problem, we extend Maliar and Maliar (2015)’s global projection method.

Work in progress

Terms of Trade Shocks and Heterogeneous International Portfolio Positions (With Jonathan Adams) Latest version: September 2018

How do terms of trade shocks affect open economies? We use a panel of exogenous terms of trade shocks for 93 countries to estimate the dynamic effects on macroeconomic variables. We find that terms of trade shocks resemble wealth shocks: a terms of trade improvement increases consumption and investment by more than output and decreases net exports, contrary to prior evidence and standard theory. To explain this outcome, we also show that terms of trade improvements increase countries' net foreign asset position, due to valuation effects of nominal net assets. To make sense of these results, we augment a standard business cycle model with realistic international portfolio choice. We estimate the model for a large sample of countries, and show that it can replicate our empirical findings: terms of trade improvements look like wealth shocks, and their importance for business cycles is heterogeneous, depending on the country's international portfolio position.

CV

Education

University of Chicago

PhD, Economics June 2016

London School of Economics & Political Science

M.Sc. Econometrics & Mathematical Economics, with Distinction June 2008

University of Oxford

M.A. Mathematics, First Class June 2005

Full CV (pdf)

Code

pgsc

R package implementing Powell's (2017) Generalized Synthetic Control method. This allows consistent estimation of treatment effect when 1) omitted variables are not fully captured by time and unit fixed effects, and 2) treatment is non-dichotomous. The package provides functions for calculating point estimates and for hypothesis testing.
Links:    Vignette    CRAN    github page

Polygons.jl

A Julia package to provide basic functionality for manipulating value sets in dynamic and repeated games. Currently includes: cnoversions between point and normal-distance forms, inner & outer approximate set sums, convex hulls, convex unions, vector addition, plotting, and cropping
Links:    Tutorial    github page

abSan

This project implements the Abreu-Sannikov (2013) method for computing sets of equilibrium values in two-player games of complete information. Interface in R, underlying code in C++.
Links:    Manual    User guide    Source package    Windows binaries    github page

cheby

R package to provide easy & fast Chebychev approximation of arbitrary 1- and 2-dimensional functions. Also generates shape-preserving 1-dimensional approximations.
Links:    Manual    User guide    Source package    Windows binaries    github page

linBilin

R package to provide fast and accurate linear, bilinear and trilinear interpolation. Interface in R, underlying calculation in C++.
Links:    Manual    Source package    Windows binaries    github page