🔎 What Was Studied

Motivated by U.S. Secretary of Defense Robert Gates' farewell address to NATO, this article asks whether NATO burden-sharing changed between 1999 and 2010 and whether wealthier allies were bearing the defense costs of poorer allies.

📊 How the Evidence Was Measured

• Spearman rank correlation tests applied to allies' defense-spending burdens across 1999–2009, with a close look at 2010.
• Wilcoxon tests comparing allies' defense burdens against proxies for the benefits they derive from NATO.
• A constructed, broad-based security expenditure burden that combines:
• defense spending,
• UN peacekeeping contributions,
• overseas foreign assistance.
• Benefit proxies included exposed border protection, terrorism risk, economic base, and population.

🔑 Key Findings

• Spearman tests show almost no evidence that rich NATO allies shouldered the defense-spending burden of poorer allies during 1999–2009.
• In 2010, the first evidence appears that richer allies were being exploited on defense spending.
• Wilcoxon tests reveal no concordance between burdens and benefits after 2002, indicating a less cohesive alliance in which allies are not underwriting their derived benefits.
• Defense spending is motivated by benefits tied to exposed border protection and terrorism risk; benefits based on economic base and population are weaker drivers for most allies.
• Using the broader security-burden measure, evidence of exploitation of the rich by the poor begins in 2004.
• Together these patterns point to a two-tiered alliance that faces significant policy challenges.

🌍 Why It Matters

The results suggest shifting incentives within NATO: linkages between who benefits and who pays have weakened, richer allies increasingly subsidize others, and alliance cohesion is strained—raising important questions for burden-sharing policy and alliance strategy.