This page describes some academic literature that suggests a median estimate of doubling of world GDP under a regime of free global labor mobility. Much of the literature is speculative, and there are many uncertainties in all estimates. We have also included references to blog posts that critically review the estimates and point out their strengths and weaknesses. There is wide variation in the views of just how much open borders will grow the economy, even among open borders advocates. The case for open borders as presented on this website is robust to this wide range of estimates.
According to the paper Economics and Emigration: Trillion-Dollar Bills on the Sidewalk? (2011) by Michael Clemens at the Center for Global Development, open borders could lead to a one-time boost in world GDP by about 50-150%. This paper is a literature review which summarizes estimates made in numerous other papers, and does not contain any new research findings in of itself. The paper relies on the estimates of gains to world GDP from labor mobility to propose a new research agenda in labor and public economics, focusing on migration issues. The paper was referenced in a blog post by Bryan Caplan. Below is the key Table 1 of the paper:
In Table 2 of the same paper, Clemens considers the possible efficiency gains from a partial relaxation of barriers to labor mobility. Clemens writes (on page 2 of the paper, which is page 84 in the journal):
A conservative reading of the evidence in Table 2, which provides an overview of efficiency gains from partial elimination of barriers to labor mobility, suggests that the emigration of less than 5 percent of the population of poor regions would bring global gains exceeding the gains from total elimination of all policy barriers to merchandise trade and all barriers to capital flows.
Links to cited papers for the open borders estimates
|Name of paper with link||Author||Year of publication||Estimate of gain to world GDP||Location of estimate in paper|
|Efficiency and distributional implications of global restrictions on labour mobility : Calculations and policy implications (gated)||Bob Hamilton and John Whalley||1984||147.3||table 4, row 2|
|The Economic Costs to International Labor Restrictions: Revisiting the Empirical Discussion||Jonathon W. Moses and Bjorn Letnes||2004||96.5||table 5, row 4 (assume elasticity of substitution to be 1.0)|
|Efficiency Gains from the Elimination of Global Restrictions on Labour Mobility: An Analysis using a Multiregional CGE Model||Ana Marie Iregui||2005||67||table 3 (may have label 10.3 in gated versions) (first row, homogeneous labour column)|
|TFP Differences and the Aggregate Effects of Labor Mobility in the Long Run (gated)||Paul Klein and Gustavo J. Ventura||2007||121.69||table 3 (last row, efficient allocation column)|
Other work not cited by Clemens
- John Kennan wrote a paper titled Open Borders (ungated PDF) a year after Clemens’ paper came out (the original version came out in August 2012, but the paper was updated in October 2012). The data used in the paper is available at Kennan’s research page. Kennan’s calculations also suggest that open borders would more than double world GDP in the long run, though he does not derive numerical estimates for world GDP (even though his model seems detailed enough for such estimates to be obtainable). Referenced in a number of blog posts listed later in the page, but most notably in John Kennan’s open borders by Nathan Smith and Upward and downward biases in the “double world GDP” estimates of the gains of open borders by Carl Shulman.
- The Global Welfare and Poverty Effects of Rich Nation Immigration Barriers by Scott Bradford (2012). Referenced by Nathan Smith in the blog post Double World GDP? Another Economic Model of Open Borders, June 4, 2014.
Ghost of Christmas Past, a commenter on EconLog, has critiqued the “double world GDP” estimates in a number of comments, such as this comment by Ghost of Christmas Past on Caplan’s “National Egoism” post and this comment by Ghost of Christmas Past on Caplan’s persuasion bleg post.
George Borjas, an immigration economist at the Harvard Kennedy School, wrote a detailed academic critique of the estimation exercises in his book Immigration Economics. Some blog posts responding to his book are included below.
Blog posts and articles
- Upward and downward biases in the “double world GDP” estimates of the gains of open borders by Carl Shulman, Reflective Disequilibrium, January 26, 2014.
- Open Borders: The Case blog posts on doubling world GDP, some selected posts below:
- The Global Economic Impact of Open Borders: My Take by Nathan Smith, February 8, 2014, where he outlines a theoretical model to estimate the gains from open borders that relies on the efficiency gains arising from clustering in cities.
- John Kennan’s Open Borders by Nathan Smith, February 11, 2013. This is a detailed analysis of John Kennan’s paper on open borders.
- Implications of embracing low-end estimates of the global economic impact of open borders by Vipul Naik, February 6, 2014. This considers what embracing the low-range back-of-the-envelope estimates might mean for the case for open borders.
- Double World GDP? Another Economic Model of Open Borders by Nathan Smith, June 4, 2014.
- Double world GDP versus scope insensitivity, by Vipul Naik, May 10, 2012, on the Open Borders blog.
- The story behind the “double world GDP” estimates by Vipul Naik, October 10, 2012, on the Open Borders blog.
- Responses to the Borjas critique:
- Trillion Dollar Bills on the Sidewalk: The Borjas Critique by Bryan Caplan, EconLog, July 16, 2014. The comment section includes a comment by Michael Clemens.
- Note on Borjas: Non-Binding Constraints Are Not Necessary by David Henderson, EconLog, July 16, 2014.
- The Efficient, Egalitarian, Libertarian, Utilitarian Way to Double World GDP by Bryan Caplan, August 20, 2011, EconLog.
- The place premium. This concept developed by Clemens and some of his colleagues is used to estimate the income gains from full labor mobility that would accrue to people at the individual level.