Why Black Knights Only Break Sanctions When Traders Join In

📚 The Puzzle and What Was Missing

Despite expectations that third-party "sanctions busters" undermine economic sanctions, most empirical studies find little effect. A likely reason is measurement: prior research almost universally relies on Hufbauer, Schott, and Elliott's (1990) dichotomous, time-invariant "black knight" indicator, which collapses varied third‑party behavior into a single static category.

📊 New Measurement of Sanctions-Busting

A richer set of sanctions-busting variables was coded to capture three dimensions often overlooked in prior work:

• Timing of sanctions-busting trade
• Quantity (how much trade bypasses sanctions)
• Nature (politically motivated vs. commercially motivated actors)

These distinctions allow a more nuanced assessment of how different kinds of third-party responses influence sanctions outcomes.

🔍 Rival Explanations Tested

Two competing accounts of sanctions-busting were evaluated:

• Political-only account: only politically motivated "black knights" reduce sanctions success.
• Joint-effects account: commercially motivated and politically motivated sanctions busters together undermine sanctions success.

🧮 How This Was Analyzed

• Research design: competing risks survival analysis
• Empirical scope: 96 episodes of U.S.-imposed sanctions, 1950–2006
• Variables: newly coded time-varying measures of sanctions-busting (timing, quantity, nature) alongside standard controls

⚠️ Key Findings

• The classic black-knight indicator, by itself, does not make sanctions more likely to fail.
• When politically motivated black knights operate together with commercially motivated sanctions busters, a strong negative effect on sanctions success emerges.

💡 Why This Matters

• Measurement matters: treating sanctions-busting as time-varying and multidimensional reveals effects masked by static indicators.
• Policy implication: targeting or mitigating commercially driven circumvention can amplify the impact of political pressure from third parties and change sanctions’ prospects for success.

Overall, third-party responses shape sanctions outcomes in conditional ways that prior dichotomous measures have obscured; distinguishing timing, scale, and motivation of sanctions-busting alters conclusions about when and why sanctions fail.